(qn. source:Hellochampion.com)

If N > 0, is N a whole number?

(1) 3 x N is an odd number.

(2) 2 x N is an even number.



The answer is (b) i.e. statement 2 is suffiecient. But how do we get this answer?

1) 3*N is a whole number, N can be x/3 where x is a whole number not divisible , or N can be a whole number.

2) 2*N is an even number, First thing very clear here is that the number cannot have a denominator other than 2, since if it has denominator other than 2 then 2N cannot be a whole number. Now , it cannot have denominator 2 either, since 2*N cannot be even if it had 2 as denominator (which would mean odd number as numerator). So (2) is sufficient.

1. 3 x N = odd int

so N = odd int/3

is every odd int divisible by 3. Try 1, 3, 5 ... Some are some not - so N cannot be a whole no


2. 2 x N = even int

N = even int /2

Every even number has to be divisible by 2 - so N is a whole number

Statement 2 is correct

Thanks. Its much clear now.