Question

30 girls and boys have planned a picnic. There is a ratio of 3 girls to 7 boys. How manny boys are there?

Answer 1

Let the ratio constant = x
the ratio of girls and boys = 3:7
∴no.of girls = 3x
∴no.of boys = 7x
total no. of girls and boys = 30
⇒3x + 7x = 30
⇒10x = 30
⇒  x = 30/10
⇒  x = 3
∴no. of boy = 7x ⇒7*3 ⇒21.
∴ no. of boys = 21