[問題] GWD4-Q9

[kwtluck]

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

Answer:D

我怎麼算都是36/96=3/8 =>B
5/8 =>D 離我好遠喔!!

[spreewell]

三數相乘要被八整除的話，有兩種情形：1.N只要是複數即可，所以1-96中有48個是複數。2.三數其中有ㄧ數為八的倍數，1-96中有12個8的倍數
所以1跟2的情形加起來總共有60種可能。所以答案為D

[kwtluck]

原來如此....soga

**感謝spreewell大大熱情解說!!**