Question

When 6 new boys were admitted and 6 girls left from the class,the percentage of boys increased from 60%to 75%.find the original number of boys and girls in class

Answer 1

Let the number of boys and girls be x and y respectively.
Percentage of boys = 60%.
⇒ x / (x + y) = 60/100
⇒ 100 x = 60x + 60y
⇒ 40 x - 60 y = 0 ....(1)
6 boys were admitted ⇒ number of boys = (x + 6)
Percentage of boys = 75%
⇒ (x + 6) / (x + 6)+(y - 6) = 75/100
⇒ x - 3y = -24..... (2)
Solving equations (1)and (2), we get,
x = 24, y = 16.
Ans-:Therefore, original number of boys and girls are 24 and 16

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