is the remainder 1?

[sanju09]

When Y is divided by 2, is the remainder 1?

1. (-1) ^(Y+2) = -1.
2. Y is prime.


[spoiler]Source: https://gmat-math.blocked/2010/02/4gmat[/spoiler]

[gmatmachoman]

After rephrasing the question simply asks IS y is odd??

St 1:

(-1) ^(Y+2) = -1.
For this to be true, Y should be odd

ex : y = 1

(-1) ^(1+2)

=(-1) ^3

= -1

if y is even, RHS will not be -1

SO st1 is sufficient

st 2:Y is prime.

Y can be = 2, so remainder can be zero

y can be 3, remainder can be 1

Inconsistent. Insufficient
Pick A

[idmaa]

Choice 1 :-

(-1) ^(Y+2) = -1

It means that Y + 2 will be odd

It means Y will be odd as Odd + Even = Odd & Even + Even = Even

So Y /2 will always leave a remainder 1, so 1 is sufficient.

Choice 2 :- Y is prime.

Y can be 2 ,so Y % 2 = 0
Y can be 3 , so Y % 2 = 1

so Insufficient

Answer A

When Y is divided by 2, is the remainder 1?

1. (-1) ^(Y+2) = -1.
2. Y is prime.


[spoiler]Source: https://gmat-math.blocked/2010/02/4gmat[/spoiler]