The ratio of the number of boys to the number of girls in a school of 672 students is 5:7.When some new boys and girls are admitted,the number of girls increase

Question

Continuation of question :by 8

and the ratio of boys to girls changes to 3:4.Calculate the boys admitted.

 

How to solve can you show with steps

Answer 1

initially total students=672

initial ratio of no. of boys to the no. of girls=5:7  (5+7=12)

 

no. of boys = 5/12 of 672 =(5/12)*672 =280

no. of girls = 672-280 = 392

 

when new boys and girls are admitted: given 8 girls are admitted and let x no. of boys admitted

no. of girls =392+8 =400

no. of boys = 280+x

new ratio of boys to girls :

(280 +x) / 400  = 3/4

(280 +x)*4 = 3*400

1120 + 4x = 1200

    4x  = 1200-1120 

    4x =  80 

x = 80/4 = 20 boys were admitted