Question

The ratio of boys and girls in a school is 5:2.if the number of boys in the school is 150 then find the total number of students in the school

Answer 1

Let the number of boys be 5a and number of girls be 2a

According to question,

5a = 150

=> a = 30

Number of girls = 2 × 30 = 60

Total number of students = Number of boys + Number of girls

= 150 + 60

= 210

Answer 2

Let boys equal to 5x and girls equal to 2x

Given boys = 150

this means
5x = 150

x = 150/5

x = 30

Hence, girls = 2x = 2 × 30 = 60

Total number of students = 150 + 60
= 210

Method 2

by ratio and proportion method we know
$\frac{ratio}{sum \: of \: ratio} \times total \: sum \: = amount \: of \: given \: ratio$
sum of ratios = 5 + 2 = 7

boys' ratio = 5

hence,
$\frac{5}{7} \times total \: student \: = 150 \\ = > total \: student \: = 150 \times \frac{7}{5} \\ = 210$
hence total students = 210

Hope it helps dear friend ☺️✌️✌️