arjtryarjtry wrote:

Is product 2*x*5*y an even integer?

1. 2 + x + 5 + y is an even integer

2. x - y is an odd integer

1)

x and y can be integers or fractions..

x=3.5 y=1.5 is not even integer

x=3 y=2 sum is even integer

insufficient

2) x - y

x and y can be integers or fractions..

combine

x+y= odd

x-y = odd

2x= odd+odd= even

2y= odd-odd= even

2*x*5*y = even*5* even/2 = integer.

So..

C.

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