刚做完GMAT PREP的数学，有一道DS题请教。谢谢啊！

If x and y are positive integers, is xy a multiple of 8?

(1) the greatest common divisor of x and y is 10

(2) the lowest common multiple of x and y is 100

知道将(1)*(2)就知道xy=10*100

但是在判断单独是否成立时，我只会代数去试。从数论方面怎么解释啊？

e.g. （2）我的做法是：if x = 20 and y=25... then xy=500, not a multiple of 8.... but x=50 and y=100, xy=5000, a multiple of 8..

请指教！

是的。答案是c.

谢谢！