In one classroom the girl to boy ratio is 7 to 6. If there is a total of 78 children in all the classrooms combined. How many boys are there?

Question

i know the answer is 6/13=b/78 where b is 36

could you explain why this ratio doesn't work 6/7=b/78? Please

Answer 1

Hi Carolyn, the ratio of 6 /7 represent the number of boys to the number of girls in one class room. You are given a total number of boys and girls. 

 

So, your ratio has to represent how many boys to the total number of boys and girls in one classroom, or 13.

 

The proportion becomes, 6 / 13 = x / 78.

 

Cross multiply getting, 13 * x = 6 * 78

 

Divide by 13 to solve for x, or x = 36.

 

There are 36 boys in all of the classrooms and 42 girls in all of the class rooms.

 

The ratio of boys to girls in all of the classrooms is 36 / 42, or 6 / 7.

 

Questions?