Trains & Bird Puzzle || Brilliant Puzzle
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- Опубліковано 29 сер 2024
- Train A starts from city A and travels towards city B.
At the same time, train B starts from city B and it travels towards city A, on the same railway track.
At the same time, a bird strats from city A and it flies towards city B over the same railway track.
Train A runs at a constant speed of : 60 km/hr
Train B runs at a constant speed of : 90 km/hr
and the bird flies at a constant speed of : 120 km/hr
The two cities are 300 kms apart.
Train A, train B and the bird start exactly at the same time.
When the bird reaches train B, it immediately reverses it's direction and flies back towards train A.
When it reaches train A, it again reverses it's direction and flies towards train B.
the bird keeps on flying back and forth between the two trains until the two trains collide with each other.
What is the distance travelled by the bird before the collision of trains.
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Finally a puzzle I could solve before Ammar could say pause
Me too
Same here
Noice!😊😊😊
I made a geometric series and spent my 20 minutes. When I saw the solution I broke my computer. Now I have to comment this by my Smartphone.
:)
0:00
There is a story about John von Neuman involving a similar puzzle about two cyclists and a fly. The hostess at a dinner party Von Neuman was attending asked Von Neuman to solve it and he gave the correct answer after a second or two of thought. The hostess said she was disappointed that Von Neuman spotted the easy solution. "Many people try to sum the infinite series in their heads", she said. Von Neuman looked surprised. "That's how I did it", he said.
Hey Steve... i just recalled about this (i read it in my college days)... it's always fun to read the last line "That's how I did it" :) Thanks for sharing
Read it in Wikipedia of John von Neumann. Doing an infinite series in head 🤗
Really happened thing or story
@@LOGICALLYYOURS how is it infinite if the distancd is finite?
@@karthikrambhatla7465 How can it be infinite if the distance is finite?
Hi mate, since you seem to appreciate us posting other solutions I did so, even though this approach is definitely not unique, of course.
Traced an axis all along the railroad, calling it x.
Values for trains t (for x being time in hours) t1(x=0)=0 and t2(x=0)=300, thus t1(x)=60x and t2(x)=300-90x.
Collision time or Xc if t1=t2. Thus solving for 60Xc=300-90Xc giving Xc=2, thus collision takes 2 hrs.
Distance of bird=speed×collision time. Thus distance of bird=120km/h×2h=240km.
Just perfect...... in fact it's more optimal solution than what I explained, due to the fact that you bypassed the use of relative speed and simply used the basic distance & speed formula. Highly appreciated.
All Indian science students should recognise this problem from ncert physics book from 11th standard.
What if it was asked that how mny times did the bird took turn🤯
theoretically infinite.. unless the minimum distance is given at which the bird stop reversing its direction.
@Manjeet THE ATHEIST yes initial distance is given. read my comment again.
Infinite times bird 🐦 took turns
Yes
Thought of some calculations but that was too easy....I missed the fact that no matter how bird flies, distance will be same
😂😂😂☝️ I just got this puzzle in my recommendations and I started it on a wrong note. After spending almost 2 mins, i realized, I just need the time of collision as i have the speed of 🐦.
I was feeling stupid and brilliant at the same time.😂
Actually this wasn't a problem for maths lovers. The moment you said that the two train travel towards each other at different speeds, I knew that it could be solved really easily by considering their relative speeds.
I got this one right ammar good job your riddles are very trick they are great excersise for brain thanks
sorry for the delay... i missed this comment :)
Sir your solution is mind blowing really very easily I am understanding this problem
Thank u bro :)
🙂🙂 your welcome 👍👍
ANOTHER WAY TO FIND THE TIME BOTH TRAIN TRAVELS IS TO ADD UP THEIR SPEED SINCE WERE MOVING TOWARDS EACH OTHER. SO 90 +60 = 150 Km/hr
time it took to 'collide' (reach each other actually) = 300/ 150 = 2 hr , bird speed 120 km/ hr so bird distance 120 x 2 = 240 kilometers
240 km..
Because I know this puzzle earlier. Amar! Want more puzzles. Love your channel
One crazy bird to do this 🤣
Awesome explanation
Solved it using easier approach.
Got the idea looking at the figures of speeds of trains.
Nice.
I got it... happy🥳🥳🥳
I think the distance is 184.24 km because the bird is moving back and forth and till it collide.
When bird reach train B it covers 171.4 km.
When bird reverses it direction and meet train A it covers 57.12.
When it again starts from train A it covers 5.72 km and collision happens.
Hope you understand
Thank u bro
I was looking for this kind of answer for this type of question you did a great job. All others make us understand things theoretically but you made this way easier by animating it.
I appreciate the work done by u. Thank u for helping me
Thanks for your answer 😊☺️😀
Oh its so nice
Thank you for the video! All of you friends are super awesome!
Great video
Easy approach 👌👍
Can't believe I solved it😂..... Maza agaya
10 sec. It is easy but Interesting.
Thank you for this solution
I calculated right...✌
Finally something I could solve quickly. :)
Thank you for this smarter method sir
I got 240 to, but acctually its less than that if we calculate bird and train inertia (slowing down and accelerating again for bird and accelerating for trains). If accelerating at constant rates and bird and trains need 10 seconds to get to full speed, then bird will will fly little over 148 km.
I done in just a min with mind calculations... Easiest puzzle ever...😂
Could you please do a video with question “ number of trips by the bird before collision “?
You have answered that in this video but the way to prove will be interesting.
My calculations says the distance travelled by bird is 420 km
Plz tell me the error if u find any-
First just use the concept of relative speed a get the train B to rest of the speed of train A=60+90=120
And the speed of bird is 120+90=210
Speed of train B=90-90=0
So the time taken by train A to collide with train B= D/S=300/150=2h
Now the whole 2 hour's the must must be roaming from one end to another and the speed of bird is constant so we can calculate the distance travepled by the bird i.e
D=s×t
=210(relative speed of bird )×2h
=420 km
And that's my answer plz suggest me where is the issue in my answer and why hasn't he taken the relative speed of bird??
I completely understood the solution to the question, but the problem is that a bird can go and come between two trains an infinite number of times. If we consider this, the two trains will not collide. How can this problem be solved? Of course, in reality, the bird must first accelerate from zero to three times, but is there anything wrong with this simplification?
Superb
Solved it in 5 seconds.
No it will be 420 km you have to change the relative speed of bird also
Mza aaya
Thank you so much
This puzzle also featured in times of india 3-4 years ago.
And that's why I was solve it today😂.
This type of questions are asked in cat logical quant section
240km
You can explain it in more simple way.. it seems too inconvenient to understand but their is an easier way than this to find the distance
Easy 1
I did it in a different method... I just wanted to know when the Train A gets collided. Train A takes 120km to get collided for which it takes 2 hours. Then, bird's fast x hour = 240km
OKAY THIS BIRD IS FAST AF
It will be 420 km
I got ittttt yeyyyy
How can we find the total distance travelled by the bird before it reaches the second train for the second time?
@@zacharias5476 Thankyou Buddy!!
This can also be solved by taking time of travel of Train A, Train B and the bird as equal, by taking distance travelled by Train A as variable 'x'. There by distance travelled by Train B will be '300-x'. Then time of travel by Train A and Train B respectively will be:
'60/x' and '90/(300-x)'
But as earlier said the time of travel is equal for all the three...
Solving the above we get time as 2 hrs.
Taking this, distance travelled by the bird will be 2*120= 240 kms
At least I got this one right.
How many times did the bird revolve???
240
Idk man I liked my solution to a fundamentally flawed riddle. As if it's not the solution it's not a riddle it's basic math
240 kms? Am I right... dude it's easy just calculate the time taken by two trains to collide... just forget about the turning of bird... just thought it as bird keeps moving at 120 kmph for the time taken by trains to collide ... easy
..lol u got the same trick...damn am smart lol
We have already solved this as a jee aspirent - Cengage ( Kinematics) Questions
Actually the puzzle must be..how many trips bird made..same was asked in Amazon interview...
Went through the first iteration of the infinite series before I realized how silly I was being and solved it using relative speeds.
Hello! Sir can u make if you like, then post one more question of this type, I, actually do not know how to post
A merchant has 3camels, wants to cross a 1500 km wide desert, the camel can carry 1000ltrs of water but they need 1ltr/km movement, how the merchant should manage to cross the desert, and no any camel should die short of water in the desert.
If I am not wrong, this puzzle is given in the famous Physics book: Resnick Haliday
1:55 how can the bird make infinite trips?🤔
240 km
The trains never collide.
Instead, train A, train B, city A, and city B are all destroyed in the explosion caused by the infinitely fast oscillation of the bird just before 2 hours after the trains and bird start.
The bird has to turn around each time it reaches a train. How long does that take ?
bird will travel for 240 kilometers or at 120 km/hr for 2hr since time x speed = distance
What would the bird's velocity be then?
AMMAR SIR, PLEASE TELL ME HOW BIRD HAS TO MAKE INFINITE TRIPS TO COVER THE TOTAL DISTANCE
Could you tell me the ans of distance travelled by bird in forward direction?
I would like to know what is the distance travelled by the bird in forward direction and backward direction separately.
forward =180kms
backward = 60kms
@@bhavikkothari8486 how do you get that?
I am preparing for jee and i got the same question in my book but their we have to calculate the no. Of times the turned 😭😭😭
what would the average velocity of the bird be then?
89mph
let the distance A travels = X then the distance B travels = 300 - x
since speed = distance x times then A travel in X/ 60 and B 300- X / 90
cross multiply will give you 90 X = 1800- 60 X or 150 X = 1800
solving for X = 120 ,
so train A travels for 120 miles and train B for 240 miles
since both train reach at the same time from when they started and collided the time is 120/60 or 180/ 90= 2hrs.
Since it took the train 2 hours to collide, it also took the bird 2 hours ...
Since the bird was travelling at 120 kilometers per hour, then in 2 hours the bird will travel
2 x 120 since DISTANCE = SPEED X TIMES AND 2 X120 = 240 KILOMETERS .. ANSWER
The real question is how can I use the bird to travel between cities since it flies faster than the faster train.
SIR USING SAME SITUATIO WHERE SPEED OF THE
BIRD NOT GIVEN. BIRD STARTS FROM TRAIN A AND GO TO B. WHAT IS THE SPEED OF THE BIRD
How can we find the no. of trips taken by the bird
At the end of the 2nd hour, train A would have travelled 120km while B travelled 180 km... Since total distance is 300 km, the trains will crash at the end of the 2nd hour... Our bird is will also be flying 2 hours before the collision at the speed of 120 km/hr... Hence 240km
The bird doesn't fly at a constant 120 Km. It has to slow and stop for a moment every time it changes direction.
hc Verma question
What if asked how many trips has the bird completed.
How many rounds did the bird take from a to b and b to a
Sir, think logically after two hours 1st train will travel 120 km and the 2nd train will travel 180km then how is it possible? That they collide,even if they are 60km away from each other?
are seriously asking this?
Oh man. Where is it mentioned that they are 60 km apart? It would be better if you clearly listen the question and then solution before you comment
The trains are traveling toward each other. If one train travels 120 km and the second travels 180 km and they get to the same point at the same time (colliding), then they had to start 120 km + 180 km = 300 km apart. 300 km is the distance given between them at the start of the puzzle.
@@SgtSupaman nicely explain , rather than taunting on someone's lower understanding
Infinite distance travell karega
No.of Times the bird touched the trains ??
I feel like something is missing in solution or may be I'm wrong but my answer is 236.734 km.
Comment before watching the video!
Ans: (300)(120)/(60+90)
I want to collab with you. If u interested plz reply.
what? if the speed of bird is different in both direction
Sir its not the distance the bird travel but its the displacement
Yash Patel Wah wah Einstein.. kya baat hai.. choti choti cheezein pakad raha hai.. ab jao aapne scalars aur vectors ke saath khelo...
@@tan_k heheh
No. Distance travelled by bird is 240 km and displacement is 120 km
I am right
My girlfriend was right, i complicate things unnecessarily.
n=∞
∑ 1600/(7*21^n) is the distance
n=0
The collision occurred 120 km from A
240 km is the displacement not distance..
I don't use any equation but got the 240 by simple logic
Wtf i was hoping you would tell the number of dird flying round alo😑😑
Stupid bird, fly higher
😂
😂
You are wrong
BRUH...
DO U EVEN KNOW HOW TO RE-ARANGE FORMULAS?!?
Speed=distance over time so...
Time=speed multiplied by distance
AND NOT DIVIDE!
bhai konsa nasha kia hai...??? agar nahi kia to 10 ki books dobara padhle
240km
240