求投掷两枚骰子所得的点数之积能被5整除的概率是多少?

您好,所有组合排列如下
1X1=1,1X2=2,1X3=3,1X4=4,1X5=5,1X6=6
2X2=4,2X3=6,2X4=8,2X5=10,2X6=12
3X3=9,3X4=12,3X5=15,3X6=18
4X4=16,4X5=20,4X6=24
5X5=25,5X6=30
6X6=36
由此可见,有21种排法,又说点数之积被5整除的概率1X5=5,2X5=10,3X5=15,4X5=20, 5X5=25,5X6=30有6种,所以就是6/21约分,也就是概率为2/7