Question

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answer both (6 and 7)

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Answer 1

Question:-

1) In a class of 40 pupils the number of girls is three-fifths of the number of boys . Find the number of boys in the class

2) After 15 years , Mary's age will be 4 times of her present age. Find her present age

Solution :

1) Given :

Total no of pupils in a class = 40

Let the no of boys be x

According to the question

The number of girls is three-fifths of the number of boys .

$\sf\green{No\:of\:Girls=\dfrac{3}{5}\:No\:of\:boys}$

$\sf\implies\:No\:of\:Girls=\dfrac{3}{5}x$

Total no of pupils in a class = 40

Thus,

No of girls+ No of boys = 40

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

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

$\sf\implies\:8x=40\times5$

$\sf\implies\:x=\dfrac{40\times5}{8}$

$\tt\implies\:x=25$

Therefore, The no of boys in the class is 25

2)Let the present age of Mary's be x

After 15 years , Mary's age = x+15

According to the question:

After 15 year's , Mary's age will be 4 times of her present age.

$\sf\implies\:x+15=4x$

$\sf\implies\:3x=15$

$\sf\implies\:x=\dfrac{15}{3}$

$\sf\implies\:x=5$

Therefore, Mary's present age is 5 years

$\huge\colorbox{lime}{sᴀᴋsʜɪ࿐ ❤}$