After paying huge pile of money for books and fraud coachings, one is left with only disappointment.... But then Ravi sir with his video of Rodha Channel appears and takes away all the tensions of Quant, Lr, Di,etc and leaves us with full knowledge about each concept..... Thank you sir.... I can miss my coaching classes but never dare to forget watching your video even on a single day💝💝
*Two common doubts:* 1. *Reverse is not true* It means all prime numbers will be of the form 6k+-1. But all numbers which are of the form 6k+-1 are not prime numbers. For example, if you take the prime number 13, it is of the form 6k+-1 ie, (6×2)+1 . But if you choose a random value for k, for example k=4, (6×4)+1 = 25 which is not a prime number. So that's what he means by "reverse is not true" 2. *Odd number question* They are all odd numbers. The equation for odd number is 2k-1. So if we take first term and equate, 2k-1=1, solve, k=1. For the last term, 2k-1=91, solve, k=46
Need more teachers like you. This is by far the most useful channel for CAT. I have the study material of TIME and I can say topics are covered in depth in these videos. Thanks a lot, Sir.
Same I was going through my cat books but couldn't understand any examples of those books so I came looking for explanation of these topics and was lucky enough to find this hidden gem.
For example (******+++++++) consider it as a numbers You have to find +++++++ ? For this you have no formula to add numbers by middle but we have formulae for adding from starting so Subtracting (******)from(******+++++++) You will get ++++++ thats what we need
it will get subtracted; means if you subtract (1 sqaure+ 2 square+ 3 square....10square) from (1square+ 2 square+ 3 square.......20 square) you'll get (11 square+12 square+ 13 square.......20square) because (1square+ 2square+ 3square....10 square) is common in both the equations and the they'll be cancelled out.
Sir in question 1+3+5------+ 91? You have taken it in the form of 2k-1 but odd numbers can be in the form of 2k+1 as well. So, can we take k=45 and and square 45. Can you please explain why you have taken it 2k-1 and not 2k+1? Please sir
@@nandinisatdeve13 they are all odd numbers. The equation for odd number is 2k-1. So if we take first term and equate, 2k-1=1, solve, k=1. For the last term, 2k-1=91, solve, k=46
@@aadishjain7454 No , because in 7/6 Ans is 1 (positive 1) but in 5/6 Ans is -1 (when it is divided by 6 ) or 5 ( when it is not divided by as numerator is smaller so)
Thank you so much sir, it's very helpful for us.. Sir one query why odd form no. is true for 2k -1 and not for 2k +1?. Sir, in your ques also 1+3+5+....+91. Here, we are taking 2k-1= 91 Answer is 46 and if, 2k+1= 91 Answer is 45. So we should not consider 2k +1 sir?
Sir why don't you add ppt slides in a folder for downloads. Kudos to you for your great initiative,you way of teaching and content is just amazing.Where all teachers are busy in unacedmy,you are the one who has provided free quality content.
Similarly, can I also say that all prime numbers except 2 are odd numbers(2k +/- 1) but reverse is not true? Reference :- Prime Number form - (6k +/- 1).
As per my understanding, even and odd numbers can be negative, I.e -2, -4, -6 are even numbers and -1,-3, -5 are odd numbers. Could you please share the source which states that even and odd numbers are non-negative?
Sir I'm starting of my preparation with number system, should I finish all the lecture videos (of number system) to go quizzes or should I carry them on side by side?
sir im confused in the first question of odd no. i think the no. of odd numbers will be 45 and not 46, as if we go by the formula 2k-1=91 so 2k=90 and l will be 45. please correct me if i'm wrong.
Take the example of 1001. When divided by 6, the remainder is - 1.but it is not a prime though it satisfies 6k+1. In short every prime no. can be expressed as 6k+1 or 6k-1 but every no. That can be expressed as 6k+1 or - 1 is not a prime no.
22:04 you are saying that reverse is not a prime no ................ BUT 6(5)+1 { where k = 5 , which is a reverse of 6 } = 31 , which is a prime no. .................... & 6k-1 -------- puting k=4 [ which is a reverse no. of 6 ] gives us the answer 23 , which is a prime no. ....... please answer me
Since there is no specific formula for calculation of individual squares starting from 11 upto 20, what Sir did was calculate the sum of individual squares from 1 to 20 using the standard formula and from that he subtracted the squares from 1 to 10 (again using the formula). It gives the same answer. It is just like adding 1 to 20 and subtracting 1 to 10 so that you can get addition of 11 to 20.
Sir I love ur teaching but I didn't understand last one which u have explained that 6k+1...in that whn we divide...by 6...that is if 1/6 ....remainder is 4...nd 6k divided by 6 and the remainder is k...nd how did u get the remainder s...1 nd 0 ...and next one even...6k-1...I have stucked wth these 2... really not only me....I have forwarded to my frnd even he didn't get it... could u please explain for us sir😢
You can still do that. But, you would start from 0 and go on till K=45. And you would assume that n=45 and your final answer will be wrong. So, in order to avoid mistakes we take it as 2K-1. . In case you are aware to count 0 to 45 and get n=46, then you can sure use the formula
@@tusharpardeshi2115 Many Thanks Tushar fo your reply, Yes the total numbers n come out to be 46 in both the cases. It is great to notice that you responded, it actually gives comfort that someone is at the other end. Thank you.
I have a doubt .plz someone clear it .In the question 2 of summation part . ques is 11^2 but in soln sir solved it taking 10^2.can anyone tell me why ?
Because the formula is applicable for series starting from 1 so he is considering at first 1-20 and from that subtracting the first 10 terms to get the actual answer.
Can anyone pls explain me 8:52 question 2, 11²+12² ? I didn't get it why sir didn't multiple 20 with 20 because as per formula n(n+1) so n should multiply with n correct ?
No, n(n+1) doesn't mean that n should be multiplied with n first. The bracket is solved first; which means solve (n+1) first and then multiply the answer with n. So it was solved that way. EXAMPLE: 20(20+1)= 20(21) =420.
at 22.00 he said that 25 is not a prime number thayswhy he said reverse is not true meaning all prime no. are of the form 6k±1 but all no. of the form 6k±1 are not prime
After paying huge pile of money for books and fraud coachings, one is left with only disappointment.... But then Ravi sir with his video of Rodha Channel appears and takes away all the tensions of Quant, Lr, Di,etc and leaves us with full knowledge about each concept..... Thank you sir.... I can miss my coaching classes but never dare to forget watching your video even on a single day💝💝
offline coaching at this time? or you're talking about online?
same comment in every video...
Kya is playlist m LR DI ki bhi video h?
Well said
A very big thanks to Ravi sir
A true legend
Mai to Mba ki tayyari kar raha tha ab aisa lag raha hai CAT nikal jaye ga .
*Two common doubts:*
1. *Reverse is not true*
It means all prime numbers will be of the form 6k+-1. But all numbers which are of the form 6k+-1 are not prime numbers. For example, if you take the prime number 13, it is of the form 6k+-1 ie, (6×2)+1 . But if you choose a random value for k, for example k=4, (6×4)+1 = 25 which is not a prime number. So that's what he means by "reverse is not true"
2. *Odd number question*
They are all odd numbers. The equation for odd number is 2k-1. So if we take first term and equate, 2k-1=1, solve, k=1. For the last term, 2k-1=91, solve, k=46
25 is a square of 5 so i think it's an exception
Thanks for solving
@@premmotghare4887 6*8+1=33 which factors are 3 and 11
👼🏻
Pls tell me how to decide K
Cat 2026 mark it🎯
Hi
Hello
Hello
2025*
Take rest bro
Need more teachers like you. This is by far the most useful channel for CAT. I have the study material of TIME and I can say topics are covered in depth in these videos. Thanks a lot, Sir.
yes u r right .now i think i have wasted my 55000 in time
@@anchalmehrotra9502 😧ayyo ..sad.. Did you purchase study materials?
@@sudhakarankumar9027 ha time ka mila tha
@@anchalmehrotra9502 hi bro, is this enough for ipmat
Same I was going through my cat books but couldn't understand any examples of those books so I came looking for explanation of these topics and was lucky enough to find this hidden gem.
Aaj se mera bhi favorite word "Right" ban gayi :D
Thank you sir, I am understanding the concepts very lucidly
love you i solved a freaking question myself the concept i never got in school i am doing it now for mba you are god
@all , how 11 square + 12 square+....+20 square = (1 square + 2 square+....+20 square) - (1 square + 2 square+....+10 square)
Yes I also didn't understand that question
For example
(******+++++++) consider it as a numbers
You have to find +++++++ ?
For this you have no formula to add numbers by middle but we have formulae for adding from starting so
Subtracting (******)from(******+++++++)
You will get ++++++ thats what we need
it will get subtracted; means if you subtract (1 sqaure+ 2 square+ 3 square....10square) from (1square+ 2 square+ 3 square.......20 square) you'll get (11 square+12 square+ 13 square.......20square)
because (1square+ 2square+ 3square....10 square) is common in both the equations and the they'll be cancelled out.
Cat 2024 preparation
Your explaination is super sir
ek saal bad mene suru kiya ha sir. thanku so much ❤️
Thankyou from Uttar Pradesh Gorakhpur
His first example is how I did my maths all my life lmao
Yess I'm a beginner!!! I really find your videos are very useful to us..Thank youu so much sir❤️✨️
Also me
Hi..
I'm a fresher as well, are these videos enough for CAT?
Hii kya apke sare rodha UA-cam lecture ke notes hai kya please send me
@@sn4480Hii kya apke sare rodha UA-cam lecture ke notes hai kya please send me
2 video not understand
This channel is a holy grail. Thank you so much sir.
Sir in question 1+3+5------+ 91? You have taken it in the form of 2k-1 but odd numbers can be in the form of 2k+1 as well. So, can we take k=45 and and square 45. Can you please explain why you have taken it 2k-1 and not 2k+1?
Please sir
If we take 2k+1 then the k for 1 will be 0 so to make the first no counted as 1 we have taken 2k-1
Can you tell how 46 came? I am confused
@@nandinisatdeve13 they are all odd numbers. The equation for odd number is 2k-1. So if we take first term and equate, 2k-1=1, solve, k=1. For the last term, 2k-1=91, solve, k=46
@@adityatrivedi579 Hey can you tell why we can't take k=0
@@HarshSharma-wn4if we can take k equals to zero
11:15 answer will be 2475
sir it means 6k+1 not always prime number but prime nnumber always in the foarm of 6k+-1
Exactly
@@aadishjain7454 No , because in 7/6 Ans is 1 (positive 1) but in 5/6 Ans is -1 (when it is divided by 6 ) or 5 ( when it is not divided by as numerator is smaller so)
Sir, what is the utility of the 6K+1 rule for prime numbers? Where can it be used effectively?
You are one of the best teacher ❤️
Thank you very much sir 🙏🏻
5:00 16:00 18:00 21:00
very helpful concept building video, can't wait for the upcoming journey with Rodha for achieving cat25 :)
Thank you so much sir, it's very helpful for us.. Sir one query why odd form no. is true for 2k -1 and not for 2k +1?. Sir, in your ques also 1+3+5+....+91.
Here, we are taking 2k-1= 91
Answer is 46 and if, 2k+1= 91 Answer is 45. So we should not consider 2k +1 sir?
If we are considering 2K+1 then for the first term 2K+1=1,K=0 then counting the 45th term and the 0th term total terms = 46
@@aroraankita381 it means we can do with both the forms right?
@@aroraankita381 thank you so much..
Are all these videos enough for CAT preparation??please answer
Sir why don't you add ppt slides in a folder for downloads. Kudos to you for your great initiative,you way of teaching and content is just amazing.Where all teachers are busy in unacedmy,you are the one who has provided free quality content.
He is also there now
@@rehnumanaqvi7529 give link?
@@GautamSingh-sm4cw ua-cam.com/video/3q6lD5BD-W4/v-deo.html
@@rehnumanaqvi7529where is the link to download please share
@@rehnumanaqvi7529Hii kya apke sare rodha UA-cam lecture ke notes hai kya please send me
1001 is not a prime no. But it comes the form of 6×167-1
Suppose x = 5.7959595 is the number what will be x ratio ?
Before, quant was my weakest section but after watching yr videos i become more confident ✨💪.....only bcz of u sir ....😇😇😇
Tume smj aa rha h???😥
@@mitashabhardwaj7496 yes! Kyu ??
@@mitashabhardwaj7496 muje nhi aa rha hai😒 😞🥺
@@mitashabhardwaj7496hana yaar 😢samaj nahi Raha hai
Thank you so much sir u explained beautifully.... Love you sir from Assam
Sir concept ke liye aapki sirf UA-cam videos sufficient h na teeno sections ke liye?
Thank you so much sir.
Doing a great job for students who are financially weak
25 is not a prime number
Thank you sirr🙏we will support u alwayss
Well explained !!!
Thank you for your efforts.
great clarity
Well explained the best cat preparation channel in the world is Rodha. amazing work
Hey did you crack the cat ¿
@ everyone 4:36 in that sir have given an example
1+2+3+4+5+.......n = n(n+1)÷2 than how did that come plz explain me
this is the normal formula that you need to learn and through that formula..even and odd summation formula will develop!!
No one can explain better than you 🙂
😊😊😊
Similarly, can I also say that all prime numbers except 2 are odd numbers(2k +/- 1) but reverse is not true? Reference :- Prime Number form - (6k +/- 1).
I got the same question... I got all the concepts clearly except that Prime no. concept.
As per my understanding, even and odd numbers can be negative, I.e -2, -4, -6 are even numbers and -1,-3, -5 are odd numbers. Could you please share the source which states that even and odd numbers are non-negative?
For this comment I will subscribe you
How to get squares of number in 2-3 seconds ?? Where i get that video sir
Sir im giving exam in 2025 and as the vids are posted 6yrs ago, still we can follow ? or there are changes in syllabus ?
What is answer and how to solve "The sum of first consecutive 5 odd number is 197 ? How to solve it? what is its answer ?
Sir I'm starting of my preparation with number system, should I finish all the lecture videos (of number system) to go quizzes or should I carry them on side by side?
Sir first of all your lectures are superbly awesome.. I am preparing for ipmat will this video's work ryt...
Thank you so much sir for your guidance ☺️
Thanxx sir for free cat coaching
Can someone tell me what he explained in the last minutes about "reverse is not true"
Please. It just went above my head
Means all prime no.s are in the form of 6k+-1 but all 6k+-1 are not prime no.s
Sir your lecture is really very helpful. Can you please suggest the book for Quantitative Aptitude?
R.S. Aggarwal Quantitative Aptitude is the best book..
Does anyone know where can we clear our doubts of quant? Any app or website or anything?
Sir please help me with how you do fast calculation?...
Voice is not clear but explanation is best
Sir how 2kplus1,2kplus3,2kplus5,2kplus7,2kplus9 are 5 consecutive odd numbers plz explain
10k + 25 = 5(2k+5) = 5 is the multiple
Thank you Sir
Can you please provide pdf link of all the lectures
Best coching
Tq so much sir its really increible teaching happy to listing &learning tqs alot sir u &my sir suggestion me.. 🙏😍guru bramaha 🙏🙏😍
Summation of even no's after taking 2 as common what will happened I don't understand
Please someone tell me
hello sir plz UA-cam Automatic Caption on kar dijiye
How 2k-1 in the fist sum with 91 as the odd number became 46
Just>>>>>
suppose we have a question for 31 square to 40 square how do we calculate those numbers?
(1^2+2^2+.......+40^2)- (1^2+2^2+.....+30^2)
Now put the formula for summation of square you will get the answer.
But why will we do that?
Can you please explain
@@rohansarda2696 can you please explain that??
@@tanvikasera6639 for getting the combination of 31^2 to 40^2
sir im confused in the first question of odd no. i think the no. of odd numbers will be 45 and not 46, as if we go by the formula 2k-1=91
so 2k=90 and l will be 45. please correct me if i'm wrong.
If we are considering 2K+1 then for the first term 2K+1=1,K=0 then counting the 45th term and the 0th term total terms = 46
@@aroraankita381 can u explain it me to more clearly I'm confused
In last method of prime no uh've said "reverse is not possible" what is the meaning of reverse in this concept??
it means if you put any value of your choice in the place of k it won't necessarily give you a prime no
Take the example of 1001. When divided by 6, the remainder is - 1.but it is not a prime though it satisfies 6k+1.
In short every prime no. can be expressed as 6k+1 or 6k-1 but every no. That can be expressed as 6k+1 or - 1 is not a prime no.
@@sidhant3912 thank u it helped me a lot😊
Thanks you for classes are in English
AT 7.22 HOW IS IT 46 ?? CAN YOU PLEASE TELL ME ?
Sir thanks for the free classes. Can you please share the link for the how to do squares video?
22:04 you are saying that reverse is not a prime no ................ BUT 6(5)+1 { where k = 5 , which is a reverse of 6 } = 31 , which is a prime no. .................... & 6k-1 -------- puting k=4 [ which is a reverse no. of 6 ] gives us the answer 23 , which is a prime no. ....... please answer me
Thank you,sir.
1sq.+2sq.= n(n+1)(2n+1)divide by 6 why these eq.is divivde by 6
16:25 sir yhn smjh kse 15 prime no hoga n 25
Hi Friends What is meant by "reverse in not true"
at 19:05 How 25 is a prime number ? Is that a mistake? Anyone please tell
he talked about it at the end of the video.
sir can you please share the video link to calculate squares and cubes that you mentioned during the video.
You are amazing Sir!
🧡🧡🧡thank you sir, huge shoutout !!!!!! one more thing, sir where is the square video? as u mentioned at
@8:00
How ro check whether 1009 is prome or not??
Whats the meaning of reverse is not true...?
Thank you so much sir 🙏🙏🙏
Thank you very much Sir🙏🙏🙏
Why is K = 46 at 7.35
Thank you sir for u r best videos
Sir, is this playlist enough for SSC aptitude ?
Sir ek query hh apne bola tha odd ke liye 2k+-1 dono use kr skte hh but in ques apne 2k-1 kiya jisme 2k-1 =92 hh hum 2k+1=92 q nhi apply kr skte isme
In the question 11^2+12^2+13^2+.......n^2
Why we took 1^+2^+...10^2
I didn’t get this
Since there is no specific formula for calculation of individual squares starting from 11 upto 20, what Sir did was calculate the sum of individual squares from 1 to 20 using the standard formula and from that he subtracted the squares from 1 to 10 (again using the formula). It gives the same answer.
It is just like adding 1 to 20 and subtracting 1 to 10 so that you can get addition of 11 to 20.
@@tusharpardeshi2115 Thank you i had the same query ..
Sir I love ur teaching but I didn't understand last one which u have explained that 6k+1...in that whn we divide...by 6...that is if 1/6 ....remainder is 4...nd 6k divided by 6 and the remainder is k...nd how did u get the remainder s...1 nd 0 ...and next one even...6k-1...I have stucked wth these 2... really not only me....I have forwarded to my frnd even he didn't get it... could u please explain for us sir😢
Hey team, why in the 1,3,5,7,9...91 example we could not take 2k + 1 ? and in this representation what is k, how could we equate to 2k-1 =91?
You can still do that. But, you would start from 0 and go on till K=45. And you would assume that n=45 and your final answer will be wrong. So, in order to avoid mistakes we take it as 2K-1.
.
In case you are aware to count 0 to 45 and get n=46, then you can sure use the formula
@@tusharpardeshi2115 Many Thanks Tushar fo your reply, Yes the total numbers n come out to be 46 in both the cases. It is great to notice that you responded, it actually gives comfort that someone is at the other end. Thank you.
Sir in question 1 + 3 + 5+______91 in this k = 1 and how 91 become k =46 please explain this
@@xgfgcv-xg1cb can you tell how u r getting 46 in both cases?
I have a doubt .plz someone clear it .In the question 2 of summation part . ques is 11^2 but in soln sir solved it taking 10^2.can anyone tell me why ?
Because the formula is applicable for series starting from 1 so he is considering at first 1-20 and from that subtracting the first 10 terms to get the actual answer.
Preparing for CAT 2021 exams ?
@@naveenkumars4132 thank you so much for explaining this 😁✌️
Can anyone pls explain me 8:52 question 2, 11²+12² ?
I didn't get it why sir didn't multiple 20 with 20 because as per formula n(n+1) so n should multiply with n correct ?
No, n(n+1) doesn't mean that n should be multiplied with n first. The bracket is solved first; which means solve (n+1) first and then multiply the answer with n. So it was solved that way. EXAMPLE: 20(20+1)= 20(21) =420.
How you calculate K=46 please explain me
2k-1=91
2k=91+1
2k=92
K=92÷2
K=46
In 1st summation question how we get k=46?
Pls answer if anyone knows !
Got it ?
@@Randomworldindia yes thankyou !
@@surabhitamrakar4184 welcome 👻
Sir ye odd no wale questions mei Ap kaise solve Kiya smjnni aya
8:34
how to get quizzes and previous year questions solved by rodha
great work sir.
Thank you. If you like the channel please share among the friends who are prepairing for CAT exam
@@Rodha give ans.
@@jaybrahmbhatt5155 for what ??
187 is not a prime no. But when it is divided by 6 it leaves remainder 1. So this 6k+1 theory isn't working here.
I told all prime nos. are of the form 6k+-1 , reverse is not true.
5:07
Thanku so much sir ❤️
Can anyone explain what is meant by "the reverse is not true" when explaining 6k +/- 1?
only one condition is possible either + or - 1
Heartly thankful to you sir
Sir iam not clear about the line
The reverse is not true in 6k+_1
What does it mean explain me sir
Get going sir...very useful videos..ever seen..
U got any college
but 25 is not a prime number.
at 22.00 he said that 25 is not a prime number thayswhy he said reverse is not true meaning
all prime no. are of the form 6k±1 but all no. of the form 6k±1 are not prime
22:00