Question

. It took Erin the same time to drive 21 miles as it took Brent to drive 15 miles. Erin's speed was 10 mph
faster than Brent's speed. How fast did Erin drive?

Answer 1

The speed at which Erin drove from the given parameters was calculated as; 35 mph

How to work with speed rates?

Let Erin's speed rate be X. Now, since it took erin 21 miles, then;

Erin's time = 21/X

Now, erin's speed was 10 mph faster than Brent's speed. Thus;

Brent's speed = (X - 10) mph

Thus, Brents time = 15/(x - 10)

Now, since they took the same time, then we know that;

21/x = 15/(x - 10)

15x = 21x - 210

6x = 210

x = 210/6

x = 35

Thus, Erins speed = 35 mph

Read more about rates at; https://brainly.com/question/12242745