Question

The average speed to go by car from home to college is 30 miles per hour. The average speed to go back home from college is 20 miles per hour because of traffic. If the college is 60 miles from home, what is the average speed for the entire round trip? What is the average speed if the college is 40 miles from home?

Answer 1

24 mph for both 60 miles and 40 miles.

Explanation:

We need to find how long it takes to get to college and from it.

Speed x time (x) = Distance (60)

30x = 60

x=2

It takes two hours to get to college

20x = 60

x = 3

It takes 3 hours to get back. It's a total of 5 hours, 2 hours at 30mph and 3 at 20. Now we need to find the average

30+30+20+20+20=120

120/5= 24

The average speed for the round trip is 24.

To do the second part, we follow the same process, but replace 60 with 40 for distance.

30x=40

x= 1.33

20x=40

x=2

We can add the total distance and divide by total time to find the average.

The total distance is 80. Time is 3.33

80/3.33=24

The average speed is still 24.