Average age of 30 girls is 1, year. average of first 18 girls is 15, year. Find out average age of r

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The average age of $30$ girls is $1\, year.$ The average of first $18$ girls is $15\, year.$ Find out the average age of remaining $12$ girls?

A

$12$

B

$10$

C

$16$

D

$10.5$

Solution

Total age of $30$ girls $=30 \times 13=390$ years

Total age of $18$ girls $=18 \times 15=270$ years

Average age of remaining $12$ girls $=\frac{390-270}{12}=\frac{120}{12}=10$ years

Standard 13

Quantitative Aptitude

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