Question

一个三位整数包含数字 $1$ 、 $3$ 、 $5$ 各一次。这个整数能被 $5$ 整除的概率是多少？

A three-digit integer contains one of each of the digits $1,$ $3,$ and $5.$ What is the probability that the integer is divisible by $5$ ?

$\dfrac{1}{6}$

$\dfrac{1}{3}$

$\dfrac{1}{2}$

$\dfrac{2}{3}$

$\dfrac{5}{6}$

这个数以 $1$ 、 $3$ 或 $5$ 结尾的可能性相同。

只有当末位是 $5$ 时，它才能被 $5$ 整除，概率为 $\dfrac{1}{3}$ 。

所以正确答案是 B。

The number is equally likely to end in $1$ , $3$ , or $5$ .

It is divisible by $5$ only if the last digit is $5$ , which happens with probability $\dfrac{1}{3}$ .

Thus, B is the correct answer.