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primes and divisibility 2

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by Gurpinder » Wed Aug 11, 2010 8:14 am
if y is an integer, is y^3 divisible by 9?

(1) y is divisible by 4
(2) y is divisible by 6

Again, I got the right answer but unsure of whether my approach is right. Please explain this.
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by selango » Wed Aug 11, 2010 8:24 am
stmt1,

y=4a

y^3=64*a^3

We don't know abt value of a.

Insuff

stmt2,

y=6a

y^3=216*a^3

y^3=24*a^3

Whatever value of a,y^3 is divisible by 9

Suff

Pick B
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by arora007 » Wed Aug 11, 2010 8:27 am
Gurpinder wrote:if y is an integer, is y^3 divisible by 9?

(1) y is divisible by 4
(2) y is divisible by 6

Again, I got the right answer but unsure of whether my approach is right. Please explain this.

the answer is B,

if we were to solve it....
1) take y=4 the answer is No take y=12 the answer is yes so INSUFF
2) y=2*3*x so y^3 = 2*2*2*3*3*3*x^3 so its but natural that y^3 is divisible by 9.
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