Question

Forty percent of a class of 40 students were boys. Suppose 25% of the girls left and five boys joined the class, find the number of boys and the number of girls now.

Answer 1

ans=40%of 40 =16

so no of boys=16

no of girl =24

25%of 24 girls left the class

25%of 24=6

now no of girls=18

and no of boys=16+5=21

Answer 2

➤ Given :-

Total students :- 40

Percentage of boys :- 40%

Percent of gírls left :- 25%

Number of boys joíned :- 5

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➤ To Find :-

The total number of boys and gírls in the class.

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★ How to do :-

Here, we are given with the total number of students in a class and the percent of boys in that class. We are also given that 25% of the gírls leave the class and five boys joín the class. Then, we are asked to find the total number of boys and gírls after joíning and leaving the class. So, first we should find the number of boys. Then, we can find the number of gírls. Next, we can find the new number of boys and gírls by applying the given number of students. So, let's solve!!

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➤ Solution :-

Number of boys :-

${\tt \leadsto 40 \bf\% \tt \: \: of \: \: 40}$

Write the percentage as fraction and the 'of' as multiplication sign.

${\tt \leadsto \dfrac{40}{100} \times 40}$

Write the denominator and the whole number in lowest form by cancellation method.

${\tt \leadsto \dfrac{40}{\cancel{100}} \times \cancel{40} = \dfrac{40}{5} \times 2}$

Now, multiply the remaining numbers.

${\tt \leadsto \dfrac{40 \times 2}{5} = \dfrac{80}{5}}$

Simplify the fraction to get the number of boys.

${\tt \leadsto \cancel \dfrac{80}{5} = 16}$

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Number of gírls :-

${\tt \leadsto 40 - 16}$

Subtract the values to get the number of gírls.

${\tt \leadsto 24 \: \: girls}$

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Number of boys (new) :-

${\tt \leadsto 16 + 5}$

Add the values to get the answer.

${\tt \leadsto \pink{\underline{\boxed{\tt 21 \: \: boys}}}}$

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Number of decreased gírls :-

${\tt \leadsto 25 \bf\% \: \: \tt of \: \: 24}$

Write the percentage as fraction and the 'of' as multiplication sign.

${\tt \leadsto \dfrac{25}{100} \times 24}$

Write the denominator and the whole number in lowest form by cancellation method.

${\tt \leadsto \dfrac{25}{\cancel{100}} \times \cancel{24} = \dfrac{25}{25} \times 6}$

Now, multiply the remaining numbers.

${\tt \leadsto \dfrac{25 \times 6}{25} = \dfrac{150}{25}}$

Simplify the fraction to get the decreased value of gírls.

${\tt \leadsto \cancel \dfrac{150}{25} = 6}$

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Number of gírls (new) :-

${\tt \leadsto 24 - 6}$

Subtract the values to get the new number of girls.

${\tt \leadsto \pink{\underline{\boxed{\tt 18 \: \: girls}}}}$

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Hence solved !!