题目
If x and y are each randomly chosen from the integers 1, 2, 3, 4, and 5, what is the probability that the product xy will be greater than 10 ?
解析
x 有 5 种选择,y 有 5 种选择,因此选取 x 和 y 的总组合数为 5 × 5 = 25 种。
在这 25 组 (x, y) 组合中,有以下 8 组的乘积大于 10:
x = 3,y = 4
x = 4,y = 3
x = 4,y = 4
x = 5,y = 3
x = 3,y = 5
x = 5,y = 4
x = 4,y = 5
x = 5,y = 5
因此,所求概率为 8/25。
答案:D。