Question

约翰逊老师的数学班中，男生与女生的比例是 $2$ 比 $3$ 。班上一共有 $30$ 名学生。男生占全班的百分之几？

There are $2$ boys for every $3$ girls in Ms. Johnson’s math class. If there are $30$ students in her class, what percent of them are boys?

$12\%$

$20\%$

$40\%$

$60\%$

$66\dfrac{2}{3}\%$

每 $2$ 个男生配 $3$ 个女生，所以每 $5$ 名学生中有 $2$ 名男生

For every $2$ boys there are $3$ girls, so boys are $2$ out of every $5$ students

把 $\frac{2}{5}$ 化成百分数

Convert the fraction $\frac{2}{5}$ to a percent

男生占每 $2 + 3 = 5$ 名学生中的 $2$ 名，也就是全班的 $\frac{2}{5}$ 。全班共有 $30$ 人这一信息其实不必使用。

化成百分数， $\frac{2}{5} = 40\%$ 。

所以正确答案是 C。

Boys make up $2$ out of every $2 + 3 = 5$ students, which is $\frac{2}{5}$ of the class. The total of $30$ students is not even needed.

As a percent, $\frac{2}{5} = 40\%.$

Thus, the correct answer is C .