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Sir your way of teaching is awsm..great job sir...and one more thing sir jo apne bola tha ki bina paiso ke bhi pdai ho skti hai ..or aap jaise teacher jo itni mehnat krte hai to koi bhi baccha exam qualify kr skta hai ...big fan of u sir..👏👏👏👍👍
Sir mai hindi midiyam ka student hu aior aapki class leta hu aap ki class dekhne se mere share daut clear ho jate hai sir ji aap sach me ham sab logo ke liye bhagvan ho 🥰🥰🥰🙏
Mai itna gadhaa hu jo sirf free fire ka video dekhta raha itne din..... Kaash kaafi pehle follow kiya hota aapka channel... Very much useful... Thank you sir... Sab kuch aasaani se samaj me aa rha hai
Problems involving Time, Distance and Speed are solved based on one simple formula. Distance = Speed * Time Which implies → Speed = Distance / Time and Time = Distance / Speed Let us take a look at some simple examples of distance, time and speed problems. Example 1. A boy walks at a speed of 4 kmph. How much time does he take to walk a distance of 20 km? Solution Time = Distance / speed = 20/4 = 5 hours. Example 2. A cyclist covers a distance of 15 miles in 2 hours. Calculate his speed. Solution Speed = Distance/time = 15/2 = 7.5 miles per hour. Example 3. A car takes 4 hours to cover a distance, if it travels at a speed of 40 mph. What should be its speed to cover the same distance in 1.5 hours? Solution Distance covered = 4*40 = 160 miles Speed required to cover the same distance in 1.5 hours = 160/1.5 = 106.66 mph Now, take a look at the following example: Example 4. If a person walks at 4 mph, he covers a certain distance. If he walks at 9 mph, he covers 7.5 miles more. How much distance did he actually cover? Now we can see that the direct application of our usual formula Distance = Speed * Time or its variations cannot be done in this case and we need to put in extra effort to calculate the given parameters. Let us see how this question can be solved. Solution For these kinds of questions, a table like this might make it easier to solve. DistanceSpeedTimed4td+7.59t Let the distance covered by that person be ‘d’. Walking at 4 mph and covering a distance ‘d’ is done in a time of ‘d/4’ IF he walks at 9 mph, he covers 7.5 miles more than the actual distance d, which is ‘d+7.5’. He does this in a time of (d+7.5)/9. Since the time is same in both the cases → d/4 = (d+7.5)/9 → 9d = 4(d+7.5) → 9d=4d+30 → d = 6. So, he covered a distance of 6 miles in 1.5 hours. Example 5. A train is going at 1/3 of its usual speed and it takes an extra 30 minutes to reach its destination. Find its usual time to cover the same distance. Solution Here, we see that the distance is same. Let us assume that its usual speed is ‘s’ and time is ‘t’, then DistanceSpeedTimedst mindS+1/3t+30 min s*t = (1/3)s*(t+30) → t = t/3 + 10 → t = 15. So the actual time taken to cover the distance is 15 minutes. Note: Note the time is expressed in terms of ‘minutes’. When we express distance in terms of miles or kilometers, time is expressed in terms of hours and has to be converted into appropriate units of measurement. Solved Questions on Trains Example 1. X and Y are two stations which are 320 miles apart. A train starts at a certain time from X and travels towards Y at 70 mph. After 2 hours, another train starts from Y and travels towards X at 20 mph. At what time do they meet? Solution Let the time after which they meet be ‘t’ hours. Then the time travelled by second train becomes ‘t-2’. Now, Distance covered by first train+Distance covered by second train = 320 miles 70t+20(t-2) = 320 Solving this gives t = 4. So the two trains meet after 4 hours. Example 2. A train leaves from a station and moves at a certain speed. After 2 hours, another train leaves from the same station and moves in the same direction at a speed of 60 mph. If it catches up with the first train in 4 hours, what is the speed of the first train? Solution Let the speed of the first train be ‘s’. Distance covered by the first train in (2+4) hours = Distance covered by second train in 4 hours Therefore, 6s = 60*4 Solving which gives s=40. So the slower train is moving at the rate of 40 mph. Questions on Boats/Airplanes For problems with boats and streams, Speed of the boat upstream (against the current) = Speed of the boat in still water - speed of the stream [As the stream obstructs the speed of the boat in still water, its speed has to be subtracted from the usual speed of the boat] Speed of the boat downstream (along with the current) = Speed of the boat in still water + speed of the stream [As the stream pushes the boat and makes it easier for the boat to reach the destination faster, speed of the stream has to be added] Similarly, for airplanes travelling with/against the wind, Speed of the plane with the wind = speed of the plane + speed of the wind Speed of the plane against the wind = speed of the plane - speed of the wind Let us look at some examples. Example 1. A man travels at 3 mph in still water. If the current’s velocity is 1 mph, it takes 3 hours to row to a place and come back. How far is the place? Solution Let the distance be ‘d’ miles. Time taken to cover the distance upstream + Time taken to cover the distance downstream = 3 Speed upstream = 3-1 = 2 mph Speed downstream = 3+1 = 4 mph So, our equation would be d/2 + d/4 = 3 → solving which, we get d = 4 miles. Example 2. With the wind, an airplane covers a distance of 2400 kms in 4 hours and against the wind in 6 hours. What is the speed of the plane and that of the wind? Solution Let the speed of the plane be ‘a’ and that of the wind be ‘w’. Our table looks like this: DistanceSpeedTimeWith the wind2400a+w4Against the wind2400a-w6 4(a+w) = 2400 and 6(a-w) = 2400 Expressing one unknown variable in terms of the other makes it easier to solve, which means a+w = 600 → w=600-a Substituting the value of w in the second equation, a-w = 400 a-(600-a) = 400 → a = 500 The speed of the plane is 500 kmph and that of the wind is 100 kmph.
Problems involving Time, Distance and Speed are solved based on one simple formula. Distance = Speed * Time Which implies → Speed = Distance / Time and Time = Distance / Speed Let us take a look at some simple examples of distance, time and speed problems. Example 1. A boy walks at a speed of 4 kmph. How much time does he take to walk a distance of 20 km? Solution Time = Distance / speed = 20/4 = 5 hours. Example 2. A cyclist covers a distance of 15 miles in 2 hours. Calculate his speed. Solution Speed = Distance/time = 15/2 = 7.5 miles per hour. Example 3. A car takes 4 hours to cover a distance, if it travels at a speed of 40 mph. What should be its speed to cover the same distance in 1.5 hours? Solution Distance covered = 4*40 = 160 miles Speed required to cover the same distance in 1.5 hours = 160/1.5 = 106.66 mph Now, take a look at the following example: Example 4. If a person walks at 4 mph, he covers a certain distance. If he walks at 9 mph, he covers 7.5 miles more. How much distance did he actually cover? Now we can see that the direct application of our usual formula Distance = Speed * Time or its variations cannot be done in this case and we need to put in extra effort to calculate the given parameters. Let us see how this question can be solved. Solution For these kinds of questions, a table like this might make it easier to solve. DistanceSpeedTimed4td+7.59t Let the distance covered by that person be ‘d’. Walking at 4 mph and covering a distance ‘d’ is done in a time of ‘d/4’ IF he walks at 9 mph, he covers 7.5 miles more than the actual distance d, which is ‘d+7.5’. He does this in a time of (d+7.5)/9. Since the time is same in both the cases → d/4 = (d+7.5)/9 → 9d = 4(d+7.5) → 9d=4d+30 → d = 6. So, he covered a distance of 6 miles in 1.5 hours. Example 5. A train is going at 1/3 of its usual speed and it takes an extra 30 minutes to reach its destination. Find its usual time to cover the same distance. Solution Here, we see that the distance is same. Let us assume that its usual speed is ‘s’ and time is ‘t’, then DistanceSpeedTimedst mindS+1/3t+30 min s*t = (1/3)s*(t+30) → t = t/3 + 10 → t = 15. So the actual time taken to cover the distance is 15 minutes. Note: Note the time is expressed in terms of ‘minutes’. When we express distance in terms of miles or kilometers, time is expressed in terms of hours and has to be converted into appropriate units of measurement. Solved Questions on Trains Example 1. X and Y are two stations which are 320 miles apart. A train starts at a certain time from X and travels towards Y at 70 mph. After 2 hours, another train starts from Y and travels towards X at 20 mph. At what time do they meet? Solution Let the time after which they meet be ‘t’ hours. Then the time travelled by second train becomes ‘t-2’. Now, Distance covered by first train+Distance covered by second train = 320 miles 70t+20(t-2) = 320 Solving this gives t = 4. So the two trains meet after 4 hours. Example 2. A train leaves from a station and moves at a certain speed. After 2 hours, another train leaves from the same station and moves in the same direction at a speed of 60 mph. If it catches up with the first train in 4 hours, what is the speed of the first train? Solution Let the speed of the first train be ‘s’. Distance covered by the first train in (2+4) hours = Distance covered by second train in 4 hours Therefore, 6s = 60*4 Solving which gives s=40. So the slower train is moving at the rate of 40 mph. Questions on Boats/Airplanes For problems with boats and streams, Speed of the boat upstream (against the current) = Speed of the boat in still water - speed of the stream [As the stream obstructs the speed of the boat in still water, its speed has to be subtracted from the usual speed of the boat] Speed of the boat downstream (along with the current) = Speed of the boat in still water + speed of the stream [As the stream pushes the boat and makes it easier for the boat to reach the destination faster, speed of the stream has to be added] Similarly, for airplanes travelling with/against the wind, Speed of the plane with the wind = speed of the plane + speed of the wind Speed of the plane against the wind = speed of the plane - speed of the wind Let us look at some examples. Example 1. A man travels at 3 mph in still water. If the current’s velocity is 1 mph, it takes 3 hours to row to a place and come back. How far is the place? Solution Let the distance be ‘d’ miles. Time taken to cover the distance upstream + Time taken to cover the distance downstream = 3 Speed upstream = 3-1 = 2 mph Speed downstream = 3+1 = 4 mph So, our equation would be d/2 + d/4 = 3 → solving which, we get d = 4 miles. Example 2. With the wind, an airplane covers a distance of 2400 kms in 4 hours and against the wind in 6 hours. What is the speed of the plane and that of the wind? Solution Let the speed of the plane be ‘a’ and that of the wind be ‘w’. Our table looks like this: DistanceSpeedTimeWith the wind2400a+w4Against the wind2400a-w6 4(a+w) = 2400 and 6(a-w) = 2400 Expressing one unknown variable in terms of the other makes it easier to solve, which means a+w = 600 → w=600-a Substituting the value of w in the second equation, a-w = 400 a-(600-a) = 400 → a = 500 The speed of the plane is 500 kmph and that of the wind is 100 kmph.
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Sorry 🤣🤣
Sir plz geometry pr video bana do
Pagal hai tu pagal
sir please agr board pe likhna ha to english main lakhy sir hindi hame samjh nahi arhi ha language thanks
👋
🎉🎉
Legends watch in 2022 also.bcz there are so rare teachers like sahil sir🙏🥰
Yes madam 🐱
Lengends ko kisi ki video dekhne ki jarurat hi nhi hota 😀😃
@@vishnumanikpuri3387 to kisi ne rumhe bulya he 😅😅😅
watch 2024
Yess
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I don't want to get divert of watching other videos ur really best, ur trick of explanation is great
Aap mere life ke sabse best teacher ho... sir.. thanku so much sir... thanku so much wify study....
2024 me kon kon dekh rha hai?
Me
I am also watching in 2024.
Me
🫡 me
🙋♀️🙋♀️🙋♀️🙋♀️🙋♀️
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pro humans watching in November before 10 days to exam
😂😂😂
It's me bro😂😂
Kl ha exam dp😅
Just a day b4 exam 😊
Tum 10 din pahlaa ki bat kar rahaa ho ham to ek din pahlaa dakh rahaa hu
Thank you so much sir for your excellent explanation 👏👏
Q5 : 25 km/hr
Q6 : 33 1/3 km/hr
Q7 : 270 km
Formula for Q7 is????.... Tell me pls
@@kamalipeethala5840 pahle avg speed find karo ,then d= t×avg speed
Thnkuu so much sirr actually it was very difficult for me to understand this concept but you made it easy for me 🤗😊
Please follow me on Instagram Vishal_badgurjar_ I'd ha
Superb aap ishi tarike se point btaiye sr sbse best bat ki 0 se start Kiya is wjh se ye video m subscribe btn pr clk kiye Bina rahe hi nhi
😢
Thank you sir, this video helped in my homework , very helpful 😃😃😃
Ekdum shandar trick sir 🔥, fan ho gya 🤩
Yesterday im watching your new video..
This video watching today ..
अबि बहुत मोटी होगए बय्य...
You are the best teacher of wifistudy
0
Lagend watching in December 2021 and say "aaj to pura pad ke hi rahunga"😂😂
😂😂😂😂😂😂
Sahi pkde ho brow 😂😂
Ajjhi mai dekha hu
😍😍😍
Yes's bro exam ha 21 ko😎
Sahil sir main aapko dil se naman 🙏karta hoon और aap such me math ke चमत्कारी बाबा है😮🙏🙏🙏👌
Appreciated work👍👍
Sir, your way of teaching is really impressive. Logo bsss apne kya dikhane ke liye dislike kara. But, great job Sir 👏🏻
Aaj life Mein phaley baar koi mera concept clear ker paya h. Thank u sir..... Great teacher 👍👍👍👍
Aapse pdhke hi time and speed samjh aya itni jgh pdh li nhi samjh pai thanks Sir 🙏
Sir ! The way of teaching is great.
Sir apse better teacher koi nhi h pure youtube pr 🙏
Cadet defence academy dek jake ek baar
Sir I think you are the only teacher who teach better on utube..free of cost
Very simply explanation
Scl k Baad agar koi best math teacher hai toh ap hai . seriously u r a vry good teacher sir 🙏
SCl MATLAB ?
@@Ash_1v means school
@@zairawani3622 thanks jii
@Gagan Verma Thanks you Dear
@Gagan Verma my pleasure
Legends watch in 2023
also.bcz there are so rare teachers like sahil sir🙏🥰
Best video for this chapter... Thnx a lot sir ❤️🙏🥰
ʘ‿ʘʘ‿ʘʘ‿ʘ
भ
Your class is very amazing sir 🙏🙏🙏🙏 Superb class Sir 👌👌👌👌
Excellent Teaching...You have been helping Many Students to fulfill their dreams of getting a Government Job.
Delhi CM Arvind Kejriwal voice and your voice are little bit same 😂😂😂
@@EveryStatusHimanshuTondwal 🤣🤣
Sir your way of teaching is awsm..great job sir...and one more thing sir jo apne bola tha ki bina paiso ke bhi pdai ho skti hai ..or aap jaise teacher jo itni mehnat krte hai to koi bhi baccha exam qualify kr skta hai ...big fan of u sir..👏👏👏👍👍
@Hasnat Ahmad hahha sarcastic way u know any trick of this video will not work in this q😂😂if want solution of this u should use basic eq..
@Hasnat Ahmad it's 12 km.
Nice pic beta
Sir you are just amazing 🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏
Hatts of uh sir!!!! 👍what an amazing way and u r so energetic which make us to learn more nd more.
Hariyana police Ki tyari kr rhe ho kya aap
You Made all the concept so easy and understable 🎉thank you so much sir 😊
Fantastic sir 👌👌 great teaching style
Nice video sir thanks sir itna eassy way me padhaya apne 🙏🏻🙏🏻🙏🏻🙏🏻
Sir you make it easy for me, now I can do it...thank you so much sir.. 🙏🙏🙏
🤚🤚
Sir, because of you I started liking maths otherwise maths was my hate most subject. You made it lot's more easier for me to understand maths
Bhn English bi seekh ja
@@chetanamehdole9310 Bhaiya at least i written in English. You should try too 😊
@@northeastrisingstar.4371 🤟🤟🤟🤟😇
Please follow me on Instagram Vishal_badgurjar_ I'd ha
Congratulations sirr g...6m..
Party to banti h...
Sir mai hindi midiyam ka student hu aior aapki class leta hu aap ki class dekhne se mere share daut clear ho jate hai sir ji aap sach me ham sab logo ke liye bhagvan ho 🥰🥰🥰🙏
Ek number ke teacher 🙌🏻👍🏻
Thank you so much sir 🙏💝
Hii
Yah
bhut achi trh se aagya h sir thankuuuuuuuuu
Thnku so much sir ji❤😊bhut ache se apki math smjh me a rhi or ap aiae hi pura zero se bataiye 😅
very good class sir...thank you soooo much...aap jaise teacher se hi hum student ki sucess milte h.
Sahi
Hi
Salute to you sir, for your dedication 🙏
thankyou sir, it really helps me. I am a new person in your channel and it really good.
You are the first person in which I understood each and everything I tried lots of videos but I didn't understand anything
Sir awesome teaching method..😊it helped me a lot..
Good girl
Best ever teaching style sir salute you ❤️❤️
Sir, my 1st day your class
You are amazing sir.......
Teaching is not profession , it a is passion ,aapko dekh ke lagta h
वाह ,,, बहुत ही उम्दा तरीके से पढ़ाया सर ...सारे कंफ्यूजन दूर हो गये ...👌👌
Apka parhana mujhe best lagti he sir.... Thank you❤ 🙃
Yes
Please follow me on Instagram
Vishal_badgurjar_
Q.5) 25 km/h
Q.6)33-1/3 or 100/3 km/h
Q.7)270 km
Are right answers 😊
Bhai 2nd video ka link bhejo
@@ambarsahu2681 next video ka link?
In teeno ko solve Kar ki bej de
Nic sir ji mai math me bahut week tha but aapse reading karke mujhe aane laga. Thanx sir
Thank you so much for making my life easier 🙏
Seriously🙁 your life?
Sir you are amazing, magic, Cool, Smart Teacher😊.... great study video and best wifi study 👍 clean and clear video 👏👍👏👍
Homework solutions
Question number ~Answer
5~25
6~33 1/3
7~ 270 km👍👍👍👍
Sir Aaj first time mujhe ye chapter acche se samajh aaya .... Thanks a lot sir 🙏🏻🙏🏻🙏🏻🙏🏻
I'm just die 💜 fan.... Of your teaching Skills 💫
I was really so much confused but you cleared all doubts thank you very much
Tor Nana chandia
Ankeeta Barik hi ankeeta...can we talk
Thank u sahil sir....nice trick.
Mujje.... Aapko thank you बोलना hai... मुझे ye concept समझ nhi aata tha... Itni देखी tqb bhi nhi... Aapji देखी ek din... Sab आया अच्छे se
Such a good teacher I had never seen
You are right
Mai itna gadhaa hu jo sirf free fire ka video dekhta raha itne din.....
Kaash kaafi pehle follow kiya hota aapka channel...
Very much useful...
Thank you sir...
Sab kuch aasaani se samaj me aa rha hai
Same condition yrr
Mujhe aaj pata chala ki free fire kya hai tumhare comment ko padhne k baad.thank god i saved myself😂😂😂
@@humanbeing4918 hahahah yes you have saved yourself Mr. Smart
@@zhinkhupatkai252 bhai aap wo dialogue bol do....Manali wala aadmi bola jo...
@@shivanshujeenger2713 bhaai kaun sa dialogue... Mujhe pta nhi.. Aap hi bol d g a
You are the best teacher in the world.
बहुत ही शानदार सर जी आप तो पहले भी अब जैसे पढ़ाते है सपर👍👍👍✌️☺️
Its helpfull to South indians ...if english subtitle added on further updates....
Thanking all of you
Fantastic classes by Wi-Fi study
I'm very aggressive from this class WO WO mind blowing class
Thank sir ji🙏🙏🙏🙏
Hamare teachers itna ache se smjhate tau maths se interesting subject koi nhi lgta.
Sir u r the best maths teacher I have come across my entire life...huge respect 4r u sir..
Very fantastic sir
Your teaching idea is very well
आप सर बहुत अच्छा बताओ से समझाते हो 🙋🙋🙋
39:54 i couldn't stop laughing. No offense happens to everyone thou.
🤣🤣🤣🤣😆😆😆I watched this scene again and again
That is funny
🤣🤣🤣🤣🤣
Awesome sir
M sabko reccomend krta hu
Thank you sir. You are the best math teacher on UA-cam.
Yes
Bhut accha lga sir aap ka video 🎉🎉🎉🎉
Thankyou sooooo much sir u cleard all the doubt..
मेरा जिंदगी भर का daut दूर हो गया !
धन्यबाद सर
Very nice bhai ji.. Keep going.... (doubt)
Problems involving Time, Distance and Speed are solved based on one simple formula.
Distance = Speed * Time
Which implies →
Speed = Distance / Time and
Time = Distance / Speed
Let us take a look at some simple examples of distance, time and speed problems.
Example 1. A boy walks at a speed of 4 kmph. How much time does he take to walk a distance of 20 km?
Solution
Time = Distance / speed = 20/4 = 5 hours.
Example 2. A cyclist covers a distance of 15 miles in 2 hours. Calculate his speed.
Solution
Speed = Distance/time = 15/2 = 7.5 miles per hour.
Example 3. A car takes 4 hours to cover a distance, if it travels at a speed of 40 mph. What should be its speed to cover the same distance in 1.5 hours?
Solution
Distance covered = 4*40 = 160 miles
Speed required to cover the same distance in 1.5 hours = 160/1.5 = 106.66 mph
Now, take a look at the following example:
Example 4. If a person walks at 4 mph, he covers a certain distance. If he walks at 9 mph, he covers 7.5 miles more. How much distance did he actually cover?
Now we can see that the direct application of our usual formula Distance = Speed * Time or its variations cannot be done in this case and we need to put in extra effort to calculate the given parameters.
Let us see how this question can be solved.
Solution
For these kinds of questions, a table like this might make it easier to solve.
DistanceSpeedTimed4td+7.59t
Let the distance covered by that person be ‘d’.
Walking at 4 mph and covering a distance ‘d’ is done in a time of ‘d/4’
IF he walks at 9 mph, he covers 7.5 miles more than the actual distance d, which is ‘d+7.5’.
He does this in a time of (d+7.5)/9.
Since the time is same in both the cases →
d/4 = (d+7.5)/9 → 9d = 4(d+7.5) → 9d=4d+30 → d = 6.
So, he covered a distance of 6 miles in 1.5 hours.
Example 5. A train is going at 1/3 of its usual speed and it takes an extra 30 minutes to reach its destination. Find its usual time to cover the same distance.
Solution
Here, we see that the distance is same.
Let us assume that its usual speed is ‘s’ and time is ‘t’, then
DistanceSpeedTimedst mindS+1/3t+30 min
s*t = (1/3)s*(t+30) → t = t/3 + 10 → t = 15.
So the actual time taken to cover the distance is 15 minutes.
Note: Note the time is expressed in terms of ‘minutes’. When we express distance in terms of miles or kilometers, time is expressed in terms of hours and has to be converted into appropriate units of measurement.
Solved Questions on Trains
Example 1. X and Y are two stations which are 320 miles apart. A train starts at a certain time from X and travels towards Y at 70 mph. After 2 hours, another train starts from Y and travels towards X at 20 mph. At what time do they meet?
Solution
Let the time after which they meet be ‘t’ hours.
Then the time travelled by second train becomes ‘t-2’.
Now,
Distance covered by first train+Distance covered by second train = 320 miles
70t+20(t-2) = 320
Solving this gives t = 4.
So the two trains meet after 4 hours.
Example 2. A train leaves from a station and moves at a certain speed. After 2 hours, another train leaves from the same station and moves in the same direction at a speed of 60 mph. If it catches up with the first train in 4 hours, what is the speed of the first train?
Solution
Let the speed of the first train be ‘s’.
Distance covered by the first train in (2+4) hours = Distance covered by second train in 4 hours
Therefore, 6s = 60*4
Solving which gives s=40.
So the slower train is moving at the rate of 40 mph.
Questions on Boats/Airplanes
For problems with boats and streams,
Speed of the boat upstream (against the current) = Speed of the boat in still water - speed of the stream
[As the stream obstructs the speed of the boat in still water, its speed has to be subtracted from the usual speed of the boat]
Speed of the boat downstream (along with the current) = Speed of the boat in still water + speed of the stream
[As the stream pushes the boat and makes it easier for the boat to reach the destination faster, speed of the stream has to be added]
Similarly, for airplanes travelling with/against the wind,
Speed of the plane with the wind = speed of the plane + speed of the wind
Speed of the plane against the wind = speed of the plane - speed of the wind
Let us look at some examples.
Example 1. A man travels at 3 mph in still water. If the current’s velocity is 1 mph, it takes 3 hours to row to a place and come back. How far is the place?
Solution
Let the distance be ‘d’ miles.
Time taken to cover the distance upstream + Time taken to cover the distance downstream = 3
Speed upstream = 3-1 = 2 mph
Speed downstream = 3+1 = 4 mph
So, our equation would be d/2 + d/4 = 3 → solving which, we get d = 4 miles.
Example 2. With the wind, an airplane covers a distance of 2400 kms in 4 hours and against the wind in 6 hours. What is the speed of the plane and that of the wind?
Solution
Let the speed of the plane be ‘a’ and that of the wind be ‘w’.
Our table looks like this:
DistanceSpeedTimeWith the wind2400a+w4Against the wind2400a-w6
4(a+w) = 2400 and 6(a-w) = 2400
Expressing one unknown variable in terms of the other makes it easier to solve, which means
a+w = 600 → w=600-a
Substituting the value of w in the second equation,
a-w = 400
a-(600-a) = 400 → a = 500
The speed of the plane is 500 kmph and that of the wind is 100 kmph.
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Best video Sir before watching it I was not able to solve the questions of time and distance
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Sir thanks apke trick se mera time , distance and speed doubt clear ho gaya
Great Teacher... Thank you sir...very nice concept
Thank you for clearing all the doubts...
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Kay Mr rhi ho
Problems involving Time, Distance and Speed are solved based on one simple formula.
Distance = Speed * Time
Which implies →
Speed = Distance / Time and
Time = Distance / Speed
Let us take a look at some simple examples of distance, time and speed problems.
Example 1. A boy walks at a speed of 4 kmph. How much time does he take to walk a distance of 20 km?
Solution
Time = Distance / speed = 20/4 = 5 hours.
Example 2. A cyclist covers a distance of 15 miles in 2 hours. Calculate his speed.
Solution
Speed = Distance/time = 15/2 = 7.5 miles per hour.
Example 3. A car takes 4 hours to cover a distance, if it travels at a speed of 40 mph. What should be its speed to cover the same distance in 1.5 hours?
Solution
Distance covered = 4*40 = 160 miles
Speed required to cover the same distance in 1.5 hours = 160/1.5 = 106.66 mph
Now, take a look at the following example:
Example 4. If a person walks at 4 mph, he covers a certain distance. If he walks at 9 mph, he covers 7.5 miles more. How much distance did he actually cover?
Now we can see that the direct application of our usual formula Distance = Speed * Time or its variations cannot be done in this case and we need to put in extra effort to calculate the given parameters.
Let us see how this question can be solved.
Solution
For these kinds of questions, a table like this might make it easier to solve.
DistanceSpeedTimed4td+7.59t
Let the distance covered by that person be ‘d’.
Walking at 4 mph and covering a distance ‘d’ is done in a time of ‘d/4’
IF he walks at 9 mph, he covers 7.5 miles more than the actual distance d, which is ‘d+7.5’.
He does this in a time of (d+7.5)/9.
Since the time is same in both the cases →
d/4 = (d+7.5)/9 → 9d = 4(d+7.5) → 9d=4d+30 → d = 6.
So, he covered a distance of 6 miles in 1.5 hours.
Example 5. A train is going at 1/3 of its usual speed and it takes an extra 30 minutes to reach its destination. Find its usual time to cover the same distance.
Solution
Here, we see that the distance is same.
Let us assume that its usual speed is ‘s’ and time is ‘t’, then
DistanceSpeedTimedst mindS+1/3t+30 min
s*t = (1/3)s*(t+30) → t = t/3 + 10 → t = 15.
So the actual time taken to cover the distance is 15 minutes.
Note: Note the time is expressed in terms of ‘minutes’. When we express distance in terms of miles or kilometers, time is expressed in terms of hours and has to be converted into appropriate units of measurement.
Solved Questions on Trains
Example 1. X and Y are two stations which are 320 miles apart. A train starts at a certain time from X and travels towards Y at 70 mph. After 2 hours, another train starts from Y and travels towards X at 20 mph. At what time do they meet?
Solution
Let the time after which they meet be ‘t’ hours.
Then the time travelled by second train becomes ‘t-2’.
Now,
Distance covered by first train+Distance covered by second train = 320 miles
70t+20(t-2) = 320
Solving this gives t = 4.
So the two trains meet after 4 hours.
Example 2. A train leaves from a station and moves at a certain speed. After 2 hours, another train leaves from the same station and moves in the same direction at a speed of 60 mph. If it catches up with the first train in 4 hours, what is the speed of the first train?
Solution
Let the speed of the first train be ‘s’.
Distance covered by the first train in (2+4) hours = Distance covered by second train in 4 hours
Therefore, 6s = 60*4
Solving which gives s=40.
So the slower train is moving at the rate of 40 mph.
Questions on Boats/Airplanes
For problems with boats and streams,
Speed of the boat upstream (against the current) = Speed of the boat in still water - speed of the stream
[As the stream obstructs the speed of the boat in still water, its speed has to be subtracted from the usual speed of the boat]
Speed of the boat downstream (along with the current) = Speed of the boat in still water + speed of the stream
[As the stream pushes the boat and makes it easier for the boat to reach the destination faster, speed of the stream has to be added]
Similarly, for airplanes travelling with/against the wind,
Speed of the plane with the wind = speed of the plane + speed of the wind
Speed of the plane against the wind = speed of the plane - speed of the wind
Let us look at some examples.
Example 1. A man travels at 3 mph in still water. If the current’s velocity is 1 mph, it takes 3 hours to row to a place and come back. How far is the place?
Solution
Let the distance be ‘d’ miles.
Time taken to cover the distance upstream + Time taken to cover the distance downstream = 3
Speed upstream = 3-1 = 2 mph
Speed downstream = 3+1 = 4 mph
So, our equation would be d/2 + d/4 = 3 → solving which, we get d = 4 miles.
Example 2. With the wind, an airplane covers a distance of 2400 kms in 4 hours and against the wind in 6 hours. What is the speed of the plane and that of the wind?
Solution
Let the speed of the plane be ‘a’ and that of the wind be ‘w’.
Our table looks like this:
DistanceSpeedTimeWith the wind2400a+w4Against the wind2400a-w6
4(a+w) = 2400 and 6(a-w) = 2400
Expressing one unknown variable in terms of the other makes it easier to solve, which means
a+w = 600 → w=600-a
Substituting the value of w in the second equation,
a-w = 400
a-(600-a) = 400 → a = 500
The speed of the plane is 500 kmph and that of the wind is 100 kmph.
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Sir
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