2) DS a/b terminating decimal?

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ern5231: Master | Next Rank: 500 Posts; Posts: 226; Joined: Sun Aug 09, 2009 4:34 am

by ern5231 » Fri Apr 30, 2010 9:22 pm

2) a, b are positive integers. Does a / b have a terminating decimal?
1> a = 5 ^ r, r is some positive integer
2> b = 2 ^ s, s is some positive integer

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Source: Beat The GMAT — Data Sufficiency | Fri Apr 30, 2010 9:22 pm

beat_gmat_09: Master | Next Rank: 500 Posts; Posts: 437; Joined: Sat Nov 22, 2008 5:06 amFollowed by: 1 member; Location: India; Thanked: 50 times; GMAT Score:580

by beat_gmat_09 » Fri Apr 30, 2010 9:59 pm

ern5231 wrote:2) a, b are positive integers. Does a / b have a terminating decimal?
1> a = 5 ^ r, r is some positive integer
2> b = 2 ^ s, s is some positive integer

IMO D

A - alone is not sufficient because denominator is not known.
B - not suff because numerator is not known.

combine A & B take r and s as any +ve numbers the result will always terminate.

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liferocks: Legendary Member; Posts: 576; Joined: Sat Mar 13, 2010 8:31 pmFollowed by: 1 member; Thanked: 97 times

by liferocks » Fri Apr 30, 2010 10:15 pm

My take is ans B

fraction with the lowest denominator of 2 or 5 or their power will always terminate as they are factors of 10

option 2 says the the denominator is 2^s hence sufficient but option 1 does not say anything about the denominator.Hence not sufficient

"If you don't know where you are going, any road will get you there."
Lewis Carroll

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ern5231: Master | Next Rank: 500 Posts; Posts: 226; Joined: Sun Aug 09, 2009 4:34 am

by ern5231 » Sun May 02, 2010 1:22 pm

OA is B

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