Question

At a local preschool, there is a ratio of 3 boys to every 4 girls. If there are 245 total preschoolers enrolled, how many boys are there

Answer 1

A ratio can be written in three different ways: 3 to 4, 3:4, and 3/4

What does this mean? It means that for every group of 7 students (3+4) there are 3 boys and 4 girls. And how many groups do we have? We have:

245/7= 35 We have 35 groups, and we just said that each group has 3 boys and 4 girls:

35*3= 105 boys

35*4= 140 girls

_ _ _---------

Total: 245 students

-------------------------------------

Here's how to set up an equation:

Let's call the number of girls x. Since the total is 245 students, 245-x= boys:

 

Set up the equation by writing the number of students in the ratio as a fraction:

3/4= (245-x)/x Cross multiply:

3x= 4(245-x) Multiply on right:

3x= 980-4x Add 4x on both sides:

7x= 980 Divide both sides by 7:

x= 140 this is how many girls there are. And:

245-140= 105= boys