Question

A school has 630 students. The ratio of the number of boys to the number of girls is 3:2. This ratio changes to 7:5 after the admission of 90 new students. Find the number of newley admited boys

Answer 1

let the original number of boys be 3x and the girls be 2x
3x+2x=630
5x=630
x=630/5
x=126

therefore number of boys = 3*126= 378 boys

now let the new number of boys be 7y and girls be 5y
7y+5y=630+90
12y=720
y=720/12
y=60
therefore boys = 7y = 7*60 = 420

therefore number of new boys = total ( new number of boys and old number of boys) - old number of boys
= 420-378
=42 boys

Therefore the newly admitted boys were 42 new boys

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