Question

The time needed to travel a certain distancevaries inversely with the rate of speed. If ittakes 8 hours to travel a certain distance at 36miles per hour, how long will it take to travel thesame distance at 60 miles per hour?

Answer 1

We know that

• It takes 8 hours to travel a certain distance at 36 miles per hour.

,

• At 60 miles per hour, how long would it take?

We solve this problem using the rule of three, or proportions. The image below shows the given relations.

We form the proportion. We have to write down 60 as numerator because it has an inverse relationship, that is, the more speed the least time needed.

$\begin{gathered} \frac{8}{x}=\frac{60}{36} \\ x=\frac{36\cdot8}{60} \\ x=\frac{288}{60} \\ x=4.8 \end{gathered}$

Therefore, it would take 4.8 hours to travel the same distance at 60 miles per hour.