###
**In a primary school the average weight of male students is 65.9 kg and the average weight of female students is 57 kg. If the average weight of all the students ( both male and female ) is 60.3 kg and the number of male students in the school is 66, what is the number of female students in the school?**

A. 162
B. 168
C. 180
D. 112
**Answer: Option D**

## Show Answer

Solution(By Apex Team)

Let the number of female students be x
Let weight of female students = 57x
Number of male students = 66
Total weights of male students = 65.9 × 66
Average weight of all the students = 60.3 kg
Total weights of all the students = 60.3 (66 + x)
According to given information,
Then,
$\begin{array}{l}\text{⇒ 60.3 (66 + x) = 66 × 65.9 + 57x}\\
\text{⇒ 60.3 × 66 + 60.3x = 66 × 65.9 + 57x}\\
\text{⇒ 60.3x – 57x = 66 (65.9 – 60.3)}\\
\text{⇒ 3.3x = 66 × 5.6}\\
\begin{aligned}\therefore&\mathrm{x}=\frac{66\times5.6}{3.3}\\
\Rightarrow&\mathrm{x}=2\times56\\
\Rightarrow&\mathrm{x}=112\end{aligned}\end{array}$

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