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In a school with 600 students, the average age of the boys is 12 years and that of the girls is 11 years. If the average age of the school is 11 years and 9 months, then the number of girls in the school is
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- 450
- 150
- 250
- 350
- 450
Correct Option: B
Let the number of girls = y
And Number of boys = 600 – y
According to question ,
| ∴ (600 – y ) × 12 + 11y = 11 | 3 | × 600 = | 47 | × 600 |
| 4 | 4 |
⇒ 7200 – 12y + 11y = 7050
⇒ y = 7200 – 7050 = 150
Hence , the number of girls is 150.
