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GMAT Prep DS Question

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GMAT Prep DS Question

by jrbrown2 » Wed Jul 18, 2007 12:18 pm
When positive integer n is divided by 3, the remainder is 2; and when positive integer t is divided by 5, the remainder is 3. What is the remainder when the product nt is divided by 15 ?

(1) n- 2 is divisible by 5.

(2) t is divisible by 3.
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Source: — Data Sufficiency |
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by chatekar » Wed Jul 18, 2007 1:05 pm
From 1:

Different possible values of n are 17, 32, 47 ....
But this doesn't tell us anything about t.
t still can have diffferent values like 8, 13, 18 ....

Different combination of these numbers to calculate nt, would result in different remainders when nt is divided by 15

so [1] is not sufficient

From 2 :

t can have values like 18

Now any combination of nt divided by 15 would produce a remainder of 2

So [1] and [2] together are sufficient.

Whats the OA by the way?

Thanks
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by blah45 » Wed Jul 18, 2007 2:56 pm
first,
n = 2, 5, 8, 11, 14, 17, ....
t = 3, 8, 13, 18,

(1)
narrows n down to => 2, 17, 32, etc.
INSUFF

(2)
narrows t down to => 3, 18, etc
INSUFF

together any value of n and t from (1) and (2) => remainder when divided by 15 is 6.

SUFF => Ans (C).
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