GMAT Problem Solving Discussions

[ashishjha100]

its x*(y**2) x times y square

[ashishjha100]

Pls help............

Two no:s a&b are chosen at random from the set {1,2,3,.........5n}.Find the probability that (a^4 - b^4)is divisible by 5.

[nikdo_19]

Originally Posted by ashishjha100

Can anybody help.........

If x and y are integers and xy2 is a positive odd integer, which of the following must be true?
Ⅰ. xy is positive.
Ⅱ. xy is odd.
Ⅲ. x + y is even.
(A) Ⅰ only
(B) Ⅱ only
(C) Ⅲ only
(D) Ⅰ and Ⅱ
(E) Ⅱ and Ⅲ

Hope this helps:

Because we need xy2 as a positive odd integer, we can safely assume that x has to be a positive interger always and y can be positive or negative. Even if y is negative we will get the output as a positive integer because we have an even power to a negative integer which makes it a positive integer.

First Case xy is positive: As explained above we can have y as negative and still get xy2 as a positive interger. So 1 cannot be a possible answer. So A and D are out.

Second Case xy is Odd:
Lets assume x = 3 and y = -5
Therefore we get the equation as 3* -5 square = 3 * 25 = 75.
This satisfies the condition of having xy2 as a positive odd integer.
I tried plugging in even numbers as x or y but wasn’t able to get to a combination where xy2 is an Odd number. For example x = 2 and y = 3 then we are getting 18 as the answer which is not inline with the conclusion of xy2 being an odd positive integer. This leads me to believe that xy has to be always odd so as to get xy2 as an odd number. So we are down to B or E.

Third Case: x + y is even:
Lets assume x = 3 and y = -5. Therefore we have x + y = -2 which satisfies the condition. Even if I take y = 5 I end up getiting x+ y as an even number 8. This statement is also true. Therefore both II and III condition are true and the answer is E.

Pugs…let me know if you think y disagree with my solution.

[viswakanth4u]

can someone help me to solve this problem?

If a committee of 3 people is to be selected from among 5 married couples so that the committee does not include two people who are married to each other, how many such committees are possible?

1. 1. A. 20

1. 1. B. 40
      
   2. C. 50
      
   3. D. 80
      
   4. E. 120

[viswakanth4u]

One more..

Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day. If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper A, which of the following expresses r in terms of p?

A. 100p / (125 – p) B. 150p / (250 – p) C. 300p / (375 – p) D. 400p / (500 – p) E. 500p / (625 – p)

[viswakanth4u]

One more..

Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day. If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper A, which of the following expresses r in terms of p?

A. 100p / (125 – p)
B. 150p / (250 – p)
C. 300p / (375 – p)
D. 400p / (500 – p)
E. 500p / (625 – p)

[bhavin422]

Originally Posted by viswakanth4u

can someone help me to solve this problem?

If a committee of 3 people is to be selected from among 5 married couples so that the committee does not include two people who are married to each other, how many such committees are possible?

1. 1. A. 20

1. 1. B. 40
      
   2. C. 50
      
   3. D. 80
      
   4. E. 120

first 3 ppl out of 10 can be selected in 10, 8 , 6 ways resp so that it does not include married couple and arrangement of these selected ppl is not important

Hence total ways = 10*8*6/ 3! = 80 ways..

[ashishjha100]

Originally Posted by viswakanth4u

One more..

Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day. If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper A, which of the following expresses r in terms of p?

A. 100p / (125 – p)
B. 150p / (250 – p)
C. 300p / (375 – p)
D. 400p / (500 – p)
E. 500p / (625 – p)

is the ans D

[ashishjha100]

Originally Posted by bhavin422

first 3 ppl out of 10 can be selected in 10, 8 , 6 ways resp so that it does not include married couple and arrangement of these selected ppl is not important

Hence total ways = 10*8*6/ 3! = 80 ways..

Pls give details of the answer.........

[nikdo_19]

Last Sunday a certain store sold copies of Newspaper A for $1.00 each and copies of Newspaper B for $1.25 each, and the store sold no other newspapers that day. If r percent of the store’s revenues from newspaper sales was from Newspaper A and if p percent of the newspapers that the store sold were copies of newspaper A, which of the following expresses r in terms of p?
A. 100p / (125 – p)
B. 150p / (250 – p)
C. 300p / (375 – p)
D. 400p / (500 – p)
E. 500p / (625 – p)

Solution:

% of newspaper A sold = p
Therefore % of newspaper B = (100 – p)

Ratio of prices of newspaper A: B = 4: 5

Revenue from A = price * % sold which is = 4p
Revenue from B = 5 * (100 – p) = 500 -5p

Total Revenue = 4p + 500 – 5p
= 500 – p

Ratio of A’s revenue to the Total Revenue = 4p: 500-p
But Ratio of A’s revenue to the Total Revenue = r%

Therefore r/100 = 4p: 500-p

r = 4p * 100 / 500-p

r = 400p / 500 – p

Answer is D.