Question

The boys and girls in the college are in the ratio $3:2.$ If $20\%$of the boys and $25\%$of the girls are adults, what is the percentage of students who are not adults?

• A. $80\%$
• B. $75\%$
• C. $78\%$
• D. $50\%$

Answer 1

The correct option is C

$78\%$

Correct option:(c )$78\%$

Let the number of students in the class$=100$

We have the ratio of boys to girls$=3:2$

Let $3x$ be the number of boys and $2x$be the number of girls.

$$\begin{gathered} \Rightarrow 5x=100 \\ \Rightarrow x=\frac{100}{5}=20 \end{gathered}$$

Number of boys $=3x=3\times 20=60$

Number of girls $=2x=2\times 20=40$

Now,

$20\%$of the boys $=\frac{20}{100}\times 60=0.2\times 60=12$

$25\%$of girls $=\frac{25}{100}\times 40=0.25\times 40=10$

Total number of boys and girls who are adults$=12+10=22$

Number of boys and girls who are not adults $=100–22=78$

Thus, The percentage of students who are not adults $=\frac{78}{100}\times 100\%=78\%.$

Hence option c is the correct answer.