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Number Properties 4th Edition pg 118 : DIVISIBILITY & PRIMES

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charleslm.king
 Post subject: Number Properties 4th Edition pg 118 : DIVISIBILITY & PRIMES
 Post Posted: Mon Nov 21, 2011 10:23 am 
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Data sufficiency example: -

is N divisible by 7?
(1) N = x - y, x and y are integers
(2) x is divisible by 7, and y is not divisible by 7

The answer given is BOTH TOGETHER are SUFFICIENT but NEITHER ALONE is sufficient. N is not divisible by 7 because y is not divisible by 7 AND x - y = N.

However, for y = 0, N = x and thus is divisible by 7 (meaning neither alone are sufficient nor are they sufficient together). Am I missing something?
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jnelson0612
 Post subject: Re: Number Properties 4th Edition pg 118 : DIVISIBILITY & PRIMES
 Post Posted: Sat Dec 10, 2011 9:58 pm 
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charleslm.king wrote:
Data sufficiency example: -

is N divisible by 7?
(1) N = x - y, x and y are integers
(2) x is divisible by 7, and y is not divisible by 7

The answer given is BOTH TOGETHER are SUFFICIENT but NEITHER ALONE is sufficient. N is not divisible by 7 because y is not divisible by 7 AND x - y = N.

However, for y = 0, N = x and thus is divisible by 7 (meaning neither alone are sufficient nor are they sufficient together). Am I missing something?


Yes, 0 is divisible by 7; in fact, it is divisible by all positive integers. :-)

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