Question

Gabriella drives her car 300 miles and averages a certain speed. If the average speed had been 9mph less, she could have traveled only 240 miles in the same length of time. What is her average speed?

Answer 1

Her average speed is 45 mph

Explanation:

Let the average speed be x mph

Time taken complete the journey = distance/ average speed

Time = 300/x

Now , at 9 mph less, she could have only traveled 240 miles in same time

At 9 mph less, the average speed is x-9

so the time would be 240/x-9

since the time is same as before;

300/x = 240/x-9

Divide both sides by 60

5/x = 4/x-9

Cross multiply

5(x-9) = 4(x)

5x - 45 = 4x

5x -4x = 45

x = 45 mph