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gmat math bible-consec integers

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gmat math bible-consec integers

by vkb16 » Fri Sep 04, 2009 11:29 pm
If r and s are consecutive odd integers, is r>s?

I. r and s are prime
II. 5<r<11

OA is C, but I think its E

the explanation says "If the no.s are consecutive odds and prime, and r=7, then s must be 5, it cant be 9 since 9 isnt a prime number. Hence r>s."

My question is, why cant r be 11 or any other prime no. 7, or less than 7???
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by Nermal » Sat Sep 05, 2009 2:40 am
I think OA=C is correct. I got to the same answer before checking it out.

We have to consider the question stem carefully: it says that r and s are consecutive odd integers,
something like 3 and 5, 7 and 9,...you name it.

We are asked to find which number is greater, r or s.

Statement 1 tells us that they are prime numbers. It does not help in determining whether r is the bigger number.

This rules out answers A and D.

Statement 2 tells us that 5<r<11. So r can be - taking into account that it has to be an odd number - 7 or 9. It does not provide any information on s though.

This rules out answer B as well.

Let's see if the statements combined tell the answer.

We know that r must equal to 7 or 9. If now, according to statement 1 r and s are prime numbers r can only equal 7.
Since they are consecutive odd integers s could be either 5 or 9, but again looking at statement 1, saying they are both prime, leaves us with s=5.

We now know the values of r=7 and s=5, thus r>s.
This is sufficient to provide the answer.

Hence C is correct.
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by srivas » Sat Sep 05, 2009 8:53 pm
Yes it is C only

r and s are conscutive odd integers 1 3 5 7 9

Statement I r and s are prime 3 5 7

statement II 5<r<11 so r = 7 or 9

from both I & II

r = 7 and s = 5 (r and s are conscutive odd integers )
Gmat710,, Hyd
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