Question

In a class of 100 students, the average amount of pocket money is $₹ 35$ per student. If the average is $₹ 25$ for girls and $₹ 50$ for boys, then the number of girls in the class is

(a) 20

(b) 40

(c) 60

(d) 80

Answer 1

Let the numiver of girls in the class $=y$

$\therefore \quad$ Number of boys in the class $=100-y$

Now, $\bar{x}_1=25, n_1=y, \bar{x}_2=50, n_2=100-y$

and

$\begin{array}{llrl}\therefore  35=\frac{25 \times y+50 \times(100-y)}{100} \\\Rightarrow  3500=25 y+5000-50 y \\\Rightarrow  25 y=1500 \\\Rightarrow  y  =60\end{array}$

$\therefore$ Number of girls in the class $=60$

So, The correct option of this question will be (C).