[求助]GMATPREP幾道數學題

conquergmat

1.
            X, Y为integers,问X(Y+1)是否为even number?

(1)
            X, Y各为prime number

(2)
            Y>7

Ans: C

(1) [x,y] = [2,2] & [3,2] though fulfill requirement but results contradict each other

(2) x,y are not specified to be odd or even

together, prime>7 is always odd thus make y+1 always even, therefore x(y+1) is made always even.

兰色部分不明白

sinocheetah

(1)x=3,y=5,it is even number, x=3,y=2, it is odd number, uncertain!

wenkey0422

thanks, i was confused by "the 500 is the multiple of 100 that is closest to X and 400 is the multiple of 100 that is closest to Y" too