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Two questions..thank you!!!

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Two questions..thank you!!!

by khizarj » Fri Jun 17, 2011 7:36 am
4) If x is not equal to -y, is (x - y)/(x + y) > 1?

1. x > 0
2. y < 0

OA is E according to GMAC....


8) If (-) denotes one of two arithmetic operations, addition or multiplication, and if k is an integer, what is the value of 3 (-) k?

1. 2(-)k = 3
2. 1(-)0 = k


What I understood from the question is that, either 2 * k = 3 OR 2 + k = 3. Therefore k is either 1.5 OR 1, but since k is an integer, k must be 1. Now, we need to find 3 (-) k, which mean, either 3 + k or 3 * k. That is either 3*1 or 3+1, which is either 3 or 4, therefore 1. is insufficient?????

OA A
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by Brent@GMATPrepNow » Fri Jun 17, 2011 8:14 am
khizarj wrote:4) If x is not equal to -y, is (x - y)/(x + y) > 1?
1. x > 0
2. y < 0
Statement 1: no info about y, so NOT SUFF
Statement 2: no info about x, so NOT SUFF

Statements 1 & 2 combined: We know that x is positive and y is negative.

case a: try x = 3 and y = -1
When we plug this into the target expression, we see that (x - y)/(x + y) IS greater than 1

case b: try x = 3 and y = -5
When we plug this into the target expression, we see that (x - y)/(x + y) IS NOT greater than 1

Since we still cannot answer the target question with certainty, the answer is E
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by Brent@GMATPrepNow » Fri Jun 17, 2011 8:24 am
khizarj wrote: If (-) denotes one of two arithmetic operations, addition or multiplication, and if k is an integer, what is the value of 3 (-) k?

1. 2(-)k = 3
2. 1(-)0 = k
Statement 1: 2(-)k = 3
khizarj, your solution is almost perfect. You wrote:

Either 2 * k = 3 OR 2 + k = 3 (great)

Therefore k is either 1.5 OR 1, but since k is an integer, k must be 1 (great)

Now, we need to find 3 (-) k, which mean, either 3 + k or 3 * k (almost)

Since k must be an integer, we know that k must equal 1. We can also conclude that the operation must be addition (since multiplication yields an non-integer value for k)

So, 3 (-) k = 3+1 = 4, which means statement 1 is sufficient.

Statement 2: 1(-)0 = k

case a: (-) represents multiplication: 1 * 0 = k, which means k=0
If k=0 and (-) represents multiplication, then 3 (-) k = 3 * 0 = 0

case b: (-) represents addition: 1 + 0 = k, which means k=1
If k=0 and (-) represents addition, then 3 (-) k = 3 + 1 = 4

Since we get 2 different answers to the target question, statement 2 is not sufficient and the answer is A

Cheers,
Brent
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by anandkrish02 » Thu Apr 26, 2012 9:25 am
hi Brent@GMATPrepNow,
Can you explain why the condition of k=-1 checked.
2-(-1)=3
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by Brent@GMATPrepNow » Thu Apr 26, 2012 9:32 am
anandkrish02 wrote:hi Brent@GMATPrepNow,
Can you explain why the condition of k=-1 checked.
2-(-1)=3
Hmm, I never suggested that k could ever equal -1.

Also, your post "2-(-1)=3" suggests that subtraction is a possible operation, when the original question says that (-) denotes either addition or multiplication.

Cheers,
Brent
Last edited by Brent@GMATPrepNow on Thu Apr 26, 2012 10:02 am, edited 2 times in total.
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by ronnie1985 » Thu Apr 26, 2012 9:49 am
First Question:-
Given: x+y not = 0
S1. sign of x-y and x+y not clear, so can't ascertain if x-y/ x+y > 1
S2. Similar case
Combination also does not clarify sign of the expression so can't ascertain if the expression is >1

Second Question:-
Your method is correct.
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by anandkrish02 » Thu Apr 26, 2012 6:14 pm
Brent@GMATPrepNow wrote:
anandkrish02 wrote:hi Brent@GMATPrepNow,
Can you explain why the condition of k=-1 checked.
2-(-1)=3
Hmm, I never suggested that k could ever equal -1.

Also, your post "2-(-1)=3" suggests that subtraction is a possible operation, when the original question says that (-) denotes either addition or multiplication.

Cheers,
Brent
Hi Brent,

Thanks for your reply, actually my question was if the condition for -ve values of k be considered, in such problems. Say, in the above problem that (-) represents addition, multiplication and subtraction.

thanks,

Anand
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