GMAT Problem Solving Discussions

MBA
1427

Harneet.. I get your reasoning. Thanks a lot!

(x/y) + 1 = (x+y)/y

I) so if x 0, implies y has to be positive.
II) by your reasoning x/y > -1 can be arrived at
III) (1/x) + (1/y) = (x+y)/(xy) --> we know (x+y/y) >0 and x
Hope this helps!


I did not understand how it can be III.

In term of II (x/y) > -1

Here's my reasoning

0 so -1
Simplly moving +1 to the LHS. Not changing signs as you are moving a value not flipping the signs.

Can you explain how III is valid and confirm if my reasoning on II is alrite ?
1428

Guys - any takes on this -

4 golphers shot an average (mean) of 3.5 under par the last time they played. What is the lowest possible score (with respect to par) if no one scored worse than 2 over par?

  1. -18
  2. 3.5
  3. -14
  4. -22
  5. -3.5
1429
Guys - any takes on this -

4 golphers shot an average (mean) of 3.5 under par the last time they played. What is the lowest possible score (with respect to par) if no one scored worse than 2 over par?
  1. -18
  2. 3.5
  3. -14
  4. -22
  5. -3.5


I am getting -20 as answer...my bad luck that's not in the options 😃 are the answer options correct 😉
1430
A jar contains 30 marbles, of which 20 are red and 10 are blue. If 9 of the marbles are removed, how many of the marbles left in the jar are red?


(1) Of the marbles removed, the ratio of the number of red ones to the number of blue ones is 2 : 1.
(2) Of the first 6 marbles removed, 4 are red.

A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D EACH Statement ALONE is sufficient.
E Statements (1) and (2) TOGETHER are NOT sufficient.


Hello,

The anwser would be A

As given in the statement 1, the ratio of the removed red to blue marbles is 2:1

By this out of the removed 9 the red marbles are 6 and blues are 3

So, the left out reds in the jar are 14.

if u take the second statement,it doesn't provide any conclusion

Hence A could be the answer

Thanks,
Prakash
1431
vicky.verma Says
I am getting -20 as answer...my bad luck that's not in the options 😃 are the answer options correct ;-)


OA is -22. What was your approach ?
1432

posted it on nodr thread...thot e1 GMAT guys might get some help frm it...

"If we take all the primes less than 300, we find that there are just 62 of them:
2, 3, 5, 7, 11, 13, 17, 19, 23, 29,
31, 37, 41, 43, 47, 53, 59, 61, 67, 71
73, 79, 83, 89, 97, 101, 103, 107, 109, 113,
127, 131, 137, 139, 149, 151, 157, 163, 167, 173,
179, 181, 191, 193, 197, 199, 211, 223, 227, 229,
233, 239, 241, 251, 257, 263, 269, 271, 277, 281,
283, 293.
25 of these primes are below 100, 21 are between 100 and 200 and 16 are between 200 and 300."

also PFA the very useful tool...for solvin remainder basd ques

1433

If n is a +ve integer and n^2 is divisible by 72, then the largest +ve integer which can divide n is...

a.6
b.12
c.24
d.36
e.48

1434

Answer should be (B) - 12.

72 can be written as = 12 * 6 = 3*3*2*2*2

if n^2 is divisible by 3*3*2*2*2; then n must be divisible by 3*2*2 = 12


If n is a +ve integer and n^2 is divisible by 72, then the largest +ve integer which can divide n is...

a.6
b.12
c.24
d.36
e.48
1435
Answer should be (B) - 12.

72 can be written as = 12 * 6 = 3*3*2*2*2

if n^2 is divisible by 3*3*2*2*2; then n must be divisible by 3*2*2 = 12

I have a doubt.....u took 3(3*2*2) from 72 as it is repeating twice....but 2 is repeating 3 times in 72 so can we pick 2 2's ....for picking 2 2's it should repeat 4 times......correct me if i'm wrong....
1436
ashishjha100 Says
I have a doubt.....u took 3(3*2*2) from 72 as it is repeating twice....but 2 is repeating 3 times in 72 so can we pick 2 2's ....for picking 2 2's it should repeat 4 times......correct me if i'm wrong....


Ashish,

Why cant answer be 48.

As 48^2 is divisible by 72 and largest +ve integer which can divide 48 is 48.
1437

72 = 3*3*2*2*2

Since we have two 3s, we must pick one 3.
Since we have three 2s, we must pick two 2s. This is because, if we pick only one 2 from 72, the denominator will be left with one more 2. That's why we must assume that n actually consists of two 2s (one obtained from the denominators pair of 2s and another to divide the single 2 left behind in the denominator).

Sorry if the explanation was too "blah".. !! Couldn't help it!


ashishjha100 Says
I have a doubt.....u took 3(3*2*2) from 72 as it is repeating twice....but 2 is repeating 3 times in 72 so can we pick 2 2's ....for picking 2 2's it should repeat 4 times......correct me if i'm wrong....
1438
72 = 3*3*2*2*2

Since we have two 3s, we must pick one 3.
Since we have three 2s, we must pick two 2s. This is because, if we pick only one 2 from 72, the denominator will be left with one more 2. That's why we must assume that n actually consists of two 2s (one obtained from the denominators pair of 2s and another to divide the single 2 left behind in the denominator).

Sorry if the explanation was too "blah".. !! Couldn't help it!


I doubt how can you get from the question...whether its asking for maximum value which should satisfy all n or maximum possible value among options......
1440

yeah i concur.. the answer will change depending on whether we are asked to find the maximum value or minimum value.

chiragdua99 Says
I doubt how can you get from the question...whether its asking for maximum value which should satisfy all n or maximum possible value among options......
1441
I think the question shud be wat is the smallest +ve integer that can divide n...in which case,12 shud be the answerr....
If we are talkin about the largest integer, it cud be anything and 48 in this question....please check da question...

my explaination for 12 as an answer is...

let a=n^2
smallest a=72, which will give n=6(sqrt(2)), since n is an integer, it cant be dis
thus a=144,which gives n=12 as the minm divisor of n

This is Q no: 424 from OG 10.........OA is B
1442

For Every integer 'K' from 1 to 10, inlcusive, the kth term of a certain sequence is given by . If T is the Sum of the first 10 terms in the sequence, then T is ?

a) Greater than 2
b) between 1 and 2
c) between 1/2 and 1
d) between 1/4 and 1/2
e) less than 1/4

this is a gmat prep question and the answer which they have given seem to be dubious to me..they have given OA as D. but I wud like to go with A. can nyone explain this ?

1443
For Every integer 'K' from 1 to 10, inlcusive, the kth term of a certain sequence is given by . If T is the Sum of the first 10 terms in the sequence, then T is ?

a) Greater than 2
b) between 1 and 2
c) between 1/2 and 1
d) between 1/4 and 1/2
e) less than 1/4

this is a gmat prep question and the answer which they have given seem to be dubious to me..they have given OA as D. but I wud like to go with A. can nyone explain this ?

The sequence will be 1/2 - 1/4 +1/8 - 1/16 -------- - 1/2^10
This is a GP with CR= -1/2

Sum of terms of GP = a(1-r^n)/(1-r)
a=1/2
r=-1/2
n=10

=(1/2)(1 - 1/2^10)/(1 + 1/2)
=(2^10 - 1)/(3 * 2^10)
=(1024 - 1)/(1024*3)
app equal to 1/3 = .33(b/w 1/4 & 1/2)

Hope this helps....
1444
For Every integer 'K' from 1 to 10, inlcusive, the kth term of a certain sequence is given by . If T is the Sum of the first 10 terms in the sequence, then T is ?

a) Greater than 2
b) between 1 and 2
c) between 1/2 and 1
d) between 1/4 and 1/2
e) less than 1/4

this is a gmat prep question and the answer which they have given seem to be dubious to me..they have given OA as D. but I wud like to go with A. can nyone explain this ?


The sequence (is a geometric sequence) can be written as --
1/2 - 1/4 + 1/8 - ....... 1/1024.

The sum of n-series geometric progression is a * (1-r^(n+1)) / (1-r).
Where a - is the sequence starter.
r - is the common rate here ( / = -1/2)
n - no.of digits

subsistuting we get, 1/2 * (1 - (-1/2)^ 11) / (1+1/2)
= 1/2 * (1 + 1/2^11) * 2/3
= 1/3 * ( 1 + 1/204 is approximately 1/3 only
so the answer must be between 1/4 and 1/2 - Hence 'D' is correct
1445
The sequence (is a geometric sequence) can be written as --
1/2 - 1/4 + 1/8 - ....... 1/1024.

The sum of n-series geometric progression is a * (1-r^(n+1)) / (1-r).
Where a - is the sequence starter.
r - is the common rate here ( / = -1/2)
n - no.of digits

subsistuting we get, 1/2 * (1 - (-1/2)^ 11) / (1+1/2)
= 1/2 * (1 + 1/2^11) * 2/3
= 1/3 * ( 1 + 1/204 is approximately 1/3 only
so the answer must be between 1/4 and 1/2 - Hence 'D' is correct

alchemist,

Sum of terms of GP = a(1-r^n)/(1-r) not a * (1-r^(n+1)) / (1-r).
1446
Dopa,

Sum of terms of GP = a(1-r^n)/(1-r) not a * (1-r^(n+1)) / (1-r).


Yep - Thanks - I got the same question but wiki misguided me..even now it shows (n+1) .. any ways after referring other manuals i agree with you it is r^n not r^(n+1)... and secondly imn't dopa ;).
1447

It should be closer to 1/3 considering the GP with first term as 1/2, r= -1/2 and n=10..



For Every integer 'K' from 1 to 10, inlcusive, the kth term of a certain sequence is given by . If T is the Sum of the first 10 terms in the sequence, then T is ?

a) Greater than 2
b) between 1 and 2
c) between 1/2 and 1
d) between 1/4 and 1/2
e) less than 1/4

this is a gmat prep question and the answer which they have given seem to be dubious to me..they have given OA as D. but I wud like to go with A. can nyone explain this ?