Problem Solving

NEXT QUESTION PLZ

Hi Suresh

The questions you post here are exciting and challenging, but are you sure GMAT(even at a 99%ile difficulty level) matches questions such as these?

I doubt that. Also, where have you had the experience of 6 years as a GMAT tutor?

In any case, thanks for the effort.

axat wrote:Hi Suresh

The questions you post here are exciting and challenging, but are you sure GMAT(even at a 99%ile difficulty level) matches questions such as these?

I doubt that. Also, where have you had the experience of 6 years as a GMAT tutor?

In any case, thanks for the effort.

Hi,

Probably the initial questions in this thread are quite tough and the scope for them to appear in the GMAT may be quite low but the questions after the first 3 or 4 are definitely much within the standard of the GMAT.

By the way, I worked for TIME and CL as a mentor/content developer.

Regards

sureshbala wrote:Folks, here is the next question..


A factor of 840 is chosen at random. What is the probability that it is divisible by 15?


A. 1/4

B. 7/32

C. 1/2

D. 1/56

E. None of these

Folks, nice to see different solutions here....Anyway here is my solution

840 = 2^3 x 3 x 7 x 5

So total number of factors of 840 = 4 x 2 x 2 x 2 = 32

Now we need factors of 840 which are divisible by 15.

This means, we need factors of 840 which are in the form of 15x.

i.e. 840 must divisible by 15x

i.e. 56 must be divisible by x.

So we need to find the factors of 56.

Since 56= 2^3 x 7, factors of 56 = 4 x 2 = 8.

Hence x can take 8 values

Thus there are 8 factors of 840 which are divisible by 15.

Hence required probability = 8/32=1/4

Here is the next one.....

Two positive numbers x and y are such that their LCM = 1188 and their HCF = 12. If x + y = 240, then find the smaller of the two numbers x and y.

A. 96

B. 108

C. 84

D. 144

E. None of these

B
xy = 1188*12 = 11*9*12*12
x+y = 240
so x = 108, y=132

sureshbala wrote:

axat wrote:Hi Suresh

The questions you post here are exciting and challenging, but are you sure GMAT(even at a 99%ile difficulty level) matches questions such as these?

I doubt that. Also, where have you had the experience of 6 years as a GMAT tutor?

In any case, thanks for the effort.

Hi,

Probably the initial questions in this thread are quite tough and the scope for them to appear in the GMAT may be quite low but the questions after the first 3 or 4 are definitely much within the standard of the GMAT.

By the way, I worked for TIME and CL as a mentor/content developer.

Regards

Hi Suresh,

I used to teach at TIME ( Andhra Pradesh). Mr. J.V. Murthy was my boss.

I really loved that experience.....it's nice to see TIME being mentioned.

p2pg wrote:B
xy = 1188*12 = 11*9*12*12
x+y = 240
so x = 108, y=132

Pure Awesomeness!!

May I steal some of your thunder to present the formulaic version of this:

The Product of 2 Numbers = ( Their GCD) * ( Their LCM)

GMAT, to fudge the question, will not explicitly say GCD and LCM; so translation is a key skill in such questions.

For Example:
The greatest number that divides 100 that also divides 50 is the same as GCD

Thanks so much for this great thread! Learnt a lot of new concepts here...

I have a question. Is there a simple way of finding out 2 numbers when you have their sums and products? Or is it just trial & error? It becomes time consuming when larger numbers are involved. So wondering if you guys have a simpler approach.

Thanks!

muna_m wrote:Thanks so much for this great thread! Learnt a lot of new concepts here...

I have a question. Is there a simple way of finding out 2 numbers when you have their sums and products? Or is it just trial & error? It becomes time consuming when larger numbers are involved. So wondering if you guys have a simpler approach.

Thanks!

Hi Muna,

Trial and Error works...but I like tis technique the best:

( X + Y ) ^2 - ( X - Y) ^2 = 4XY

This way we can calculate any of the 3 expressions, when the other two are given.

Excellent questions - Thanks a lot suresh for posting these. Its certainly helping me push my brainpower upward. Its been around 10 to 12 years since I used to solve these kind of questions and my mind has rusted since then. This thread is helping me brush off some of the rust
I know that the first few questions were 900+ level and are unlikely in GMAT. But the remaining are definitely of the 780+ caliber. Some of those can occasionally slip into GMAT but its worth going through this thread for a day!!
Btw folks you can learn a lot by going through this thread as you will discover some fabulous shortcuts as you try to solve them and see the solutions. Most of the folks here are GMAT instructors and/or are in constant touch with their math roots. Most of them are CAT (not Computer Adaptive Test but Common Aptitude Test for management studies in India) veterans and CAT is 10 times more difficult than GMAT. This exercise will definitely be easy for recent college grads and math aficionados but might not be well received by people who have grown out of that puzzle solving phase (which is venerated in India during engineering days). However too much of these problems is not going to help somebody becoming a millionaire or impress a hot chic but will definitely push your GMAT score beyond a certain threshold if you are hitting the wall.
Thanks again for all the problems so far

no more 780+ questions?

Musiq wrote:

sureshbala wrote:

axat wrote:Hi Suresh

The questions you post here are exciting and challenging, but are you sure GMAT(even at a 99%ile difficulty level) matches questions such as these?

I doubt that. Also, where have you had the experience of 6 years as a GMAT tutor?

In any case, thanks for the effort.

Hi,

Probably the initial questions in this thread are quite tough and the scope for them to appear in the GMAT may be quite low but the questions after the first 3 or 4 are definitely much within the standard of the GMAT.

By the way, I worked for TIME and CL as a mentor/content developer.

Regards

Hi Suresh,

I used to teach at TIME ( Andhra Pradesh). Mr. J.V. Murthy was my boss.

I really loved that experience.....it's nice to see TIME being mentioned.

That's nice to hear...My first boss is also Mr.JVM. I learnt a lot during my career as a mentor in TIME, Vizag. I worked there from 2003-2006.

@yogami..thanks for the post...nice to hear that this thread helped you to brush up the concepts

Here is the next question....

Participation in the local soccer league this year is 10% higher than last year.The number of males increased by 5% and the number of females increased by 20%. What fraction of the soccer league is now female?

A. 1/3

B. 4/11

C. 2/5

D. 4/9

E. 1/2

C is the answer?