Ratio of people at 3 for every 7

Question

The school has 3 boys for every 7 girls. How many boys are in school if there are 200 more girls than boys? 

Answer 1

Hi Rich,

 

This is a proportion or ratio problem. The best way to handle these problems is:
   - Set it up as fractions equal to each other.
   - Be very careful where you put the numbers and variables.
   - Cross-multiply to solve.

 

Let's start with calling the total # of boys B.  That means the total # of girls is B+200

 

Now we can set up our equation:

   3/7 = B/B+200   (If you write this on paper with 3 over 7, etc., it will be easier to see how to cross-multiply.)

 

When we cross-multiply we get 3(B+200) = 7B

 

In case you need help from there ...

   3B + 600 = 7B

   600 = 4B

   150 = B

 

From there, I'm sure you can take it!  Remember to double check your answer.

 

Paul L.