Question

7.60. When Paul crossed the finish line of a 60-meter race, he was ahead of Robert by 10 meters and ahead of Sam by 20 meters. Suppose Robert and Sam continue to race to the finish line without changing their rates of speed. By how many meters will Robert beat Sam?
Hint: By how many meters would Robert beat Sam if the race were 50 meters? 100 meters? 150 meters?

Answer 1

Answer:

The number of meters Robert will beat Sam is 12 meters.

Step-by-step explanation:

Given:

When Paul crossed the finish line of a 60-meter race, he was ahead of Robert by 10 meters and ahead of Sam by 20 meters. Suppose Robert and Sam continue to race to the finish line without changing their rates of speed.

Find:

the number of meters by which Robert will beat Sam

Step 1 of 1

When Paul finishes, Robert has run 60-10=50 meters and Sam has run 60-20=40 meters.

Therefore, when Robert and Sam run for the same amount of time, Sam covers $\frac{40}{50}=\frac{4}{5}$ of the distance that Robert covers. So, while Robert runs the final 10 meters of the race, Sam runs $\frac{4}{5} \cdot 10=8$ meters.

This means Robert's lead over Sam increases by 2 more meters, and he beats Sam by 10+2=12 meters.