###
**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 of the school is 11 years 9 months, then the average the number of girls in the school is :
**

A. 150
B. 250
C. 350
D. 450
**Answer: Option A**

## Show Answer

Solution(By Apex Team)

Let the number of girls be x
Then, number of boys = (600 – x)
Then,
$\begin{array}{l}\left(11\frac{3}{4}\times600\right)=11x+12(600-x)\\
\Leftrightarrow x=7200-7050\\
\Leftrightarrow x=150\end{array}$

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