A driver would have reduced the time it took to drive from home to the store by 1/3 if the average ...

A driver would have reduced the time it took to drive from home to the store by 1/3 if the average speed had been increased by 21 miles per hour. What was the actual average speed, in miles per hour, when the driver drove from home to the store?

Quiz

Answer/Solution

42

Steps/Work

Let R be the original speed and let T be the original time.
Since the distance remains the same (we're just changing the rate and time), any increase in rate or time is met with a decrease in the other term. Decreasing the time by 1/3 would give us:
D = (R)(T) = (2T/3)(x*R)
x = 3/2 since (2T/3)(3R/2) = (R)(T) = D
3R/2 = R + 21
R/2 = 21
R= 42
The answer is B.

General Calculator / Auto Solver

A driver would have reduced the time it took to drive from home to the store by / if the average speed had been increased by miles per hour. What was the actual average speed, in miles per hour, when the driver drove from home to the store?

Calculated Answer

42

Step by Step Solution

In order to solve problem, you must evaluate ((n0 - n0 / n1) * n2) / (n0 - (n0 - n0 / n1)).

n0 =1
n1 =3
n2 =21