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Hmm anandnk, I don't think I agree with your answer. I think the answer should be C.

Quote:

What is the gcd of (2^a) - 1 and (2^b) -1

1. gcd(a, b) = 3 2. lcm(a, b) = 9

1) Insufficient. We only know that a and b have 3 in common. a could be greater than or less than b.

2) Also insufficient.
If a = 3^2 and b= 3, LCM = 3^2, then the gcd of (2^9) - 1 and (2^3) - 1 is 7.

If a = 3^2 and b = 3^2, LCM = 3^2, then the gcd of (2^9) - 1 and
(2^9) - 1 is 511.

Together,
Either a = 3^2 and b = 3 OR a = 3 and b = 3^2. Regardless, the gcd(a,b) will be 7 so the answer should be C. Both statements are sufficient together.

Last edited by Makky07 on 27 May 2004, 06:09, edited 1 time in total.

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