Question

the number of boysand girls in a class arein ratio of 7:5. thenumber of boys is 8more than girls what isthe total strength ofthe class?

Answer 1

Let girls=x
Boys= 8+x
ratio= 7:5= 8+x:x
          7x=40+5x [Product of means is equal to product of extremes]
         2x = 40
         x = 20
so, girls =x=20
      boys=8+x=8+20=28

Answer 2

This is an easy method.........
let the no. of boys be 7x
girls are 5x.(∵the ratio =7:5)
given.............
7x=5x+8
2x=8
  x=4
therefore the no. of boys = 28
                         no. of girls = 20





hope this easy method helps you
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