Question

A car moves with a speed of 30 km/h–1 for half an hour, 25 km/h–1 for one hour and 40 km/h–1 for two hours. Calculate the average speed of the car.

Answer 1

speed = 30km/h

time = 1/2h

distance

speed = 25km/h

t = 1h

distance = 25 * 1 = 25km

speed = 40km/h

t = 2h

distance = 40 * 2 = 80km

total distance = 15 + 25 + 80 = 120km

total time = 3.5h

avg speed = 120/3.5 = 34.29km/h

Answer 2

A car moves with a speed of 30 km/h for half an hour, 25 km/h for one hour, and 40 km/h for an hour and a half. How would one calculate the average speed of the car?

Calculating “speed” is based on the fundamental relationship of “distance” = “rate” X “time.”

Using algebra, you can divide both sides of this equation by “time” and get:

“rate” = “distance” / “time”

“time” is 0.5 hours + 1 hour + 1.5 hour, or 3 hours total

You can determine the distance travelled using “d = r x t.”

The first leg is 15 km ( 15 km = 30 km/hr X 0.5 hr).

The second leg is 25 km ( 25 km = 25 km/hr X 1 hr).

The third leg is 60 km ( 60 km = 40 km/hr X 1.5 hr).

The total distance is 100 km (15 + 25 +60).

The average speed is 33.3 km/hr (33.3 = 100 km / 3 hours).