Question

In a class, the ratio of girls to boys is 3: 7.

(i) What percentage of the total number of students is girls and what percentage of the total number of students is boys?

(ii) If the total number of students is 70, what would be the number of girls and what would be the number of boys in the class?

Answer 1

(i) Girls: Boys = 3: 7
Total number of parts = 3 + 7 = 10.

By unitary method:

Girls:
10 → 3(Girls)

1 → `3/10`

100 → `3/10 xx 100` = 30 Girls = 30%

Boys:

10 → 7(Boys)
1 → `7/10`

100 → `7/10 xx 100` = 70 Boys = 70%

(ii) 
In Fraction:

Girls = `3/10 xx 70 = 21`.

Boys = `7/10 xx 70 = 49`.

In Percentage:

Girls = `30/100 xx 70 = 21`.

Boys = `70/100 xx 70 = 49`.