GWD上的一道数学题，求解答

elsachialee

Q9:

If an integer n is to be chosen at random from the integers 1 to 96, inclusive, what is the probability that n(n + 1)(n + 2) will be divisible by 8?

A. 1/4  B. 3/8  C. 1/2  D. 5/8  E. 3/4
谢谢~~

luciferc

D
如果要n(n+1)(n+2)是8的倍数，也就是说，n是2的倍数，就可以了，因为n+2一定是4的倍数；或者n+1是八的倍数也可以，这个时候n和n+2都是奇数
n是2的倍数有96/2=48种；n+1是8的倍数，有96/8=12种
所以（48+12）/96=5/8

elsachialee

谢谢~~~