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x is a positive integer, is x even

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x is a positive integer, is x even

by coolgirl26 » Sun Apr 19, 2009 12:28 pm
I'm really slow at solving for these type of data sufficiency questions

Please help me increase my speed by giving me some short cut to solve problem

X is a positive integar, is x even??

1) 9x^2 is divisible by 4 (meaning that 9x2 must be a multiple of 4..right..

2) 3x+2 is diviisble by 8

what are some quick tips to solve this problem

what do you see when u solve this

how can i solve this question in a minute or less?

Please help

Answer:D
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Source: — Data Sufficiency |
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by cramya » Sun Apr 19, 2009 12:38 pm
Stmt I

9 x^2 is divisble by 4

9 is not divisible by 4 so x^2 must be divisible by 4 which means x must be diviisble by 2.

x is even

SUFF

Stmt II

3x+2 is divisible by 8


3x+2 must be even

We know 2 is even so 3x must also be even since even+even = even whereas odd+even = odd

For 3x to be even x must be even since odd*odd = odd only odd(3) * even = even

x is even

SUFF

Choose D
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Re: x is a positive integer, is x even

by iamcste » Sun Apr 19, 2009 12:41 pm
coolgirl26 wrote:I'm really slow at solving for these type of data sufficiency questions

Please help me increase my speed by giving me some short cut to solve problem

X is a positive integar, is x even??

1) 9x^2 is divisible by 4 (meaning that 9x2 must be a multiple of 4..right..


divisible by 4 means 9x^2 is even,

Square if even means 9x is also even ( Try 4 is even, 2 is even, 9 is odd, 3 is odd)

9x is even

A product is even when atleast one of them is even

hence x must be even to make 9x even

Sufficient


2) 3x+2 is diviisble by 8


divisble by 8, 3x+2 is even

An addition is even when both adding elements are same ( either both odd or even)

2 is even, so to make 3x+2 even, 3x has to be even, and to make a product even, atleast one of the element has to be even

so x is even

Sufficient

choose D

Take aways

know when a product or additon results in odd or even

A square or cube resembles the properties of the number it is square or cube of..

HTH
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