Question

Elaine drives her car 180 miles and has an average of a certain speed. If the average speed had been 5mph more, she could have traveled 200 miles in the same length of time. What was her average speed?

Answer 1

45 mph

Explanation:

Using the equation d = rt, we can rearrange the equation to be t = d/r

Since the amount of time was the same, we can set d/r equal to each other for both speeds.

Let x represent the average speed.

`(d)/(r)` =
`(d)/(r)`

`(180)/(x)` =
`(200)/(x+5)`

Cross multiply and solve for x:

200x = 180x + 900

20x = 900

x = 45

So, the average speed was 45 mph