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The average age of group of 20 girls is 15 years and that of another group of 25 boys it is 24 years. The average age of the two groups mixed together is
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- 19.5 years
- 20 years
- 21 years
- 21.5 years
- 19.5 years
Correct Option: B
According to question ,
| Required average age = |  | 20 × 15 + 25 × 24 |  | years |
| 20 + 25 |
| Required average age = | | 300 + 600 | | years |
| 45 |
| Required average age = | | 900 | | years = 20 years |
| 45 |
