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Divisibility questions - quickest way to solve?

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Divisibility questions - quickest way to solve?

by smehmood » Fri Aug 15, 2008 5:33 pm
We see lot of divisibility type of questions in GMAT as shown in the attached. What is the quickest way to solve these type of questions.
I would solve the attached by plugging different values for k and then see if it is divisible. Not sure if this is the quickest way to solve these type of questions.
Please advise.
Thanks
M
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Source: — Data Sufficiency |
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by Vignesh.4384 » Fri Aug 15, 2008 7:07 pm
Factorize .. You wil see the answer quickly
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by smehmood » Sat Aug 16, 2008 3:48 am
Thanks for the reply.
Sorry I didn't understand. Factorize what?
Could you please explain?
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by sumithshah » Sat Aug 16, 2008 11:23 am
Here are my two cents

We need to prove is k has at least powers of 2.

a) 8K is divisible by 16, that means K must have one power of 2. We need 2 powers of 2 - so since we aren't sure if k has one or more powers of 2, we can say it is insufficient

b) 9K is divisible by 12 means 3*3*K is divisible by 12, which would imply that K has atleast 2 powers of 2 ( which is basically what we need). Therefore sufficient.
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