Question

in class of 40 pupils the number of girls is three fifth of number of boys. find number of boys. ​

Answer 1

Answer:

32

Step-by-step explanation:

no. of students=40

no. of girls=1/5th

=40x1/5

=8

no. of boys=40-8

=32

Answer 2

Given :-

• In class of 40 pupils the number of girls is three-fifth of number of boys.

To Find :-

• What is the number of boys.

Solution :-

Let,

$\mapsto \bf Number\: of\: boys =\: x$

Hence, the number of girls with be :

$\bigstar$ The number of girls is three-fifth of number of boys.

$\implies \sf Number\: of\: girls =\: \dfrac{3}{5} \times Number\: of\: boys$

$\implies \sf Number\: of\: girls =\: \dfrac{3}{5} \times x$

$\implies \sf\bold{Number\: of\: girls =\: \dfrac{3x}{5}}$

According to the question,

$\implies \sf \dfrac{3x}{5} + x =\: 40$

$\implies \sf \dfrac{3x + 5x}{5} =\: 40$

By doing cross multiplication we get,

$\implies \sf 3x + 5x =\: 5(40)$

$\implies \sf 8x =\: 5 \times 40$

$\implies \sf 8x =\: 200$

$\implies \sf x =\: \dfrac{\cancel{200}}{\cancel{8}}$

$\implies \sf\bold{\purple{x =\: 25}}$

Hence, the number of boys and girls are :

❒ Number Of Boys :

$\longrightarrow \sf Number\: of\: boys =\: x$

$\longrightarrow \sf\bold{\red{Number\: of\: boys =\: 25}}$

❒ Number Of Girls :

$\longrightarrow \sf Number\: of\: Girls =\: \dfrac{3x}{5}$

$\longrightarrow \sf Number\: of\: Girls =\: \dfrac{3 \times 25}{5}$

$\longrightarrow \sf Number\: of\: Girls =\: \dfrac{\cancel{75}}{\cancel{5}}$

$\longrightarrow \sf\bold{\red{Number\: of\: Girls =\: 15}}$

${\small{\bold{\underline{\therefore\: The\: number\: of\: boys\: is\: 25\: . }}}}$

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★ VERIFICATION ★

$\implies \sf \dfrac{3x}{5} + x =\: 40$

By putting x = 25 we get,

$\implies \sf \dfrac{3 \times 25}{5} + 25 =\: 40$

$\implies \sf \dfrac{75}{5} + 25 =\: 40$

$\implies \sf 15 + 25 =\: 40$

$\implies \bf 40 =\: 40$

Hence, Verified.