Question

The ratio of boys to girls in Jamal's class is 3:2. If four more girls join the class, there will be the same number of boys and girls. What is the number of boys in the class?

Answer 1

Answer:

12 boys

Step-by-step explanation:

From the above question:

Number of boys = 3

Number of girls = 2

Boys: Girls

3:2

Let :

a = boys

b = girls

Hence, a : b = 3 : 2

a/b = 3/2  

Cross Multiply

2a = 3b .......... Equation 1

a = 3b/2

If four more girls join the class, there will be the same number of boys and girls

Hence,

a: b + 4 = 3 : 3

a/b + 4 = 3/3

Cross Multiply

3a = 3(b + 4)

3a = 3b + 12 ........ Equation (2)

From Equation 1: a = 3b/2

Substitute 3b/2 for a in Equation 2 we have:

3a = 3b + 12 .........Equation 2

3(3b/2) = 3b + 12

9b/2 = 3b + 12

Cross Multiply

9b = 2(3b + 12)

9b= 6b + 24

9b - 6b = 24

3b = 24

b = 8

Substitute 8 for b in Equation 1

a = 3b/2

a = 3 × 8/2

a = 24/2

a = 12

Therefore, the number of boys in the class is 12