A car travels a total distance of 120 miles. For the first 60 miles, the car travels at an… — GRE General Test

A car travels a total distance of $120$ miles. For the first $60$ miles, the car travels at an average speed of $30$ miles per hour, and for the remaining $60$ miles, the car travels at an average speed of $60$ miles per hour. What is the average speed of the car, in miles per hour, for the entire $120$ -mile trip?

Answer: 40 miles per hour

Answer

The average speed of the car for the entire trip is

40

miles per hour.

The overall average speed is determined by dividing total distance (

120

miles) by total time (

3

hours), yielding

40

miles per hour.

Step-by-Step Solution

Calculate time taken for the first segment

Time =

2

hours

Using

\text{Time} = \frac{\text{Distance}}{\text{Speed}}

\frac{60}{30} = 2

hours.

Calculate time taken for the second segment

Time =

1

hour

Using

\text{Time} = \frac{\text{Distance}}{\text{Speed}}

\frac{60}{60} = 1

hour.

Determine total distance and total time

Total distance =

120

miles, Total time =

3

hours

Add distances (

60 + 60 = 120

) and times (

2 + 1 = 3

Calculate overall average speed

Average speed =

40

miles per hour

Divide total distance by total time:

\frac{120}{3} = 40

Key Concept

Average Speed and Rates

Estimated Time:1m 0s

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