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0 a multiple of all numbers??? [#permalink]
01 Oct 2004, 23:07

On another site, the answer to the following Data Sufficiency:

X is a prime number. What is X?

(1) X <15

(2) (X-2) is a multiple of 5

The answer purported to be E, because X could be 2 or 7, given that 5 and 0 are multiples of 5 (i.e. each 5 and 0 can be divided by 5 evenly).

This just seems wrong - that 0 is a multiple of all numbers - but wanted to sanity check this with a considerably more sophisticated site than the one I happenned to be on when I ran across this.

1. X is a prime number < than 15. It can be 2,3,5,7,11,or 13. Diff possible values for X. Hence Insuff.
2. X-2 = multiple of 5 => cn be 5, 10, 15, 20, 25...whatever. Now, say X-2 = 5 => X=3. say, X-2 = 10 => X=12. Different values for X. Hence Insufficient.

Combining both we have. X=3 prime number or say, X=12 not a prime number. Again many different values for X. Hence Insufficient. Hence E.

Thanks Praet. Silly mistakes have costed me time and again - god help me. I will put in the error log. Its fortunate that the answer I derived is still right.