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OG Quantitative (Green) #86

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OG Quantitative (Green) #86

by mdavis » Mon Feb 02, 2009 11:48 am
Could someone explain the answer to this question?

Can the positive integer n be written as the sum of two different positive prime numbers?

(1) n is greater than 3.
(2) n is odd.
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Source: — Data Sufficiency |
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Answer is A

by peddisetty » Mon Feb 02, 2009 5:02 pm
Lets take 4(3+1), 5(3+2),6(5+1), 7(5+2), 8(5+3), 9(7+2), 10(7+3) can all be written as sum of two different prime nos. But 2 cant be written as sum of two different primes.

In A, we have n>3, so its sufficient.

B, is not sufficient. Since 1 is odd, but cant be written as sum of two different primes.

So, the answer is A.
Raj Peddisetty
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by raptor84 » Mon Feb 02, 2009 8:10 pm
IMO its E.

Take the number 11. This cant be expressed as a sum of two +ve prime numbers right.

So E.

Whats the OA?
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by mdavis » Mon Feb 02, 2009 8:37 pm
OA is E. The explanation in the book is confusing to me.
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by sacx » Tue Feb 03, 2009 4:03 am
I think it should be E

1. n > 3

Lets say its 11 - cannot be expressed as a sum of prime numbers

2. n is odd

Same example as above can be used

Comine 1 & 2, n = 11 and it fails again
SACX
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