Section 2

Explore

 

In Discover you developed strategies to help solve a ratio problem. You found a known ratio, 1:25, for lifeguards to swimmers. Then you used this ratio to find an unknown ratio, x:500.

 

One strategy to solve the problem may have been using a proportion to compare the two ratios.

 

Once a proportion is set up, you can rearrange or cross multiply to solve for x.

 

Rearrange	Cross Multiply

 

As you saw in Discover, 20 lifeguards are needed when 500 people are swimming.

 

As you have just seen, proportional reasoning helps relate one known ratio to find a missing term in another ratio. In Try This 2 you will use proportional reasoning to solve a problem.