Powerscore Test 2 Question #11 (odd/even)

[dddannie6]

If x and y are integers and x=50y+69, which of the following must be odd?

xy
x+y
x+2y
3x-1
3x+1

I choose the correct answer which was x+2y
but I cannot seem to understand why that is since when I choose numbers both b and c are coming up with odd answers.

Please help!

Best,
Dannie

[tobias.apps]

This question is testing your knowledge of the even and odd rules:
O*O=O
E*E=E
E*O=E

E+O=O
O+O=E
E+E=E

The given equation states that both x and y are integers but does not say either are even or odd so you have to assume both cases until you're given the equation x=50y+69 which is always going to be odd (50y: 50 is even and we know that an E times an odd or an even is going to be even; we also know that an E plus an odd will be odd).

So since x is always odd, you know need to test each option. x + 2y == Odd + 2*(Odd or Even) == Odd + Even == Odd.

Hope that helped.

[tommywallach]

I actually answered this question elsewhere. Please only post a question in one place, DD. Thanks!

-t