NIMCET 2016 Question Paper with solutions

Question : 55 of 120

Marks: +1, -0

The average marks of boys in class is 52 and that of girls to 42. The average marks of boys and girls combined is 50, then percentage of boys in the class is;

Validate

Solution:

Given,

x_1=52,x_2=42

and

x=50

Let

n_1

and

n_2

be the number of boys and girls respectively in the class.

∵x={n_1x_1+n_2x_2}/{n_1+n_2}

⇒50=\;\;{52(n_{1})+42n_{2}}/{n_{1}+n_{2}}

⇒50(n_{1}+n_{2})=52n_{1}+42n_{2}

⇒50n_{1}+50n_{2}=52n_{1}+42n_{2}

⇒8n_{2}=2n_{1}

⇒n_{1}=4n_{2}

So, percentage of boys

=n_1/{n_1+n_2}×100

={4n_2}/{4n_2+n_2}×100

={4n_2}/{5n_2}×100

=4/5×100=80%

Go to Question:

Prev Question

Next Question