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Basic DS- odd integer

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Basic DS- odd integer

by venmic » Tue Aug 30, 2011 12:14 am
Is the integer N odd?

1 ) N is divisible by 3
2) N i divisible by 5

other than plugging in numbers and then finding out the answer how do you work it out using variables

Appreciate your help

E
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by Geva@EconomistGMAT » Tue Aug 30, 2011 12:20 am
venmic wrote:Is the integer N odd?

1 ) N is divisible by 3
2) N i divisible by 5

other than plugging in numbers and then finding out the answer how do you work it out using variables

Appreciate your help

E
A semi-algebraic representation of the statements could follow this:

Stat. (1) N=3*integer, where the integer could be odd or even.
3*odd = odd
3*even=even

Therefore N could be odd or even.

Stat. (2) N=5*integer, where the integer could be odd or even.
5*odd = odd
5*even=even

Therefore N could be odd or even.

Combined: N = 3*5*integer = 15*integer, where the integer could be odd or even.
15*odd = odd
15*even=even

Therefore N could be odd or even.

But this really just complicates things. Variables are cumbersome for this problem. All you really need to do is show that the statements are insufficient - find examples where N is odd and not odd. 3 and 6 for stat. (1), 5 and 10 for stat. (2), 3*5 and 3*5*2 for combined.
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