-
The ratio of number of boys to that of girls in a group becomes 2:1 when 15 girls leave. But, afterwards, when 45 boys also leave, the ratio becomes 1 : 5. Originally the number of girls in
the group was
-
- 20
- 30
- 40
- 50
Correct Option: C
Let the original number of boys and girls be x and y respectively.
Then
| = | ||
| y − 15 | 1 |
⇒ x = 2y – 30 ....(i)
| Again, | = | ||
| y − 15 | 5 |
⇒ 5x – 225 = y – 15
⇒ 5x = y – 15 + 225
⇒ 5 (2y–30) = y + 210 [From equation (i)]
⇒ 10y – 150 = y + 210
⇒ 10y – y = 210 + 150
⇒ 9y = 360
| ⇒ y = | = 40 | |
| 9 |
