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The average age of 30 girls is 13 years. The average age of the first 18 girls is 15 years. Find out the average of the remaining 12 girls.
1. 15
2. 12
3. 10
4. 12.5

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Correct Answer - Option 3 : 10

Given:

The average age of 30 girls = 13

The average age of the first 13 girls = 15

Calculations:

Total age of 30 girls = 30 × 13

⇒ 390

Total age of 18 girls = 15 × 18

⇒ 270

∴ age of the remaining 12 girls = 390 – 270

⇒ 120

∴ required average = 120/12

⇒ 10 years

The average age of the remaining 12 girls is 10 years.

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