Correct Answer - Option 2 : 120
Given:
Total students = 720
Ratio of boys and girls in the art class = 7 ∶ 5
Required ratio = 1 ∶ 1
Calculation:
Ratio of boys and girls in the art class = 7 ∶ 5
Total students = 720
∴ Total number of boys = 720 × 7/12
⇒ 60 × 7
⇒ 420
∴ Total number of girls = 720 – 420
⇒ 300
Now, number of girls that should join to make ratio 1 ∶ 1
⇒ 420 – 300
⇒ 120
∴ 120 more girls should join to make the ratio 1 ∶ 1.
ALTERNATE METHOD:
Total number of students = 720
Boys : Girls = 7 : 5
No. of boys = 7/12 × 720
⇒ 420
No. of girls = 5/12 × 720
⇒ 300
Let no. of girls should join = x
420/(300 + x) = 1/1
⇒ 300 + x = 420
⇒ x = 120
∴ 120 more girls should join to make the ratio 1 ∶ 1.
