Question

Joe is on a cross-country trip from New York to Los Angeles. He drives for 45.0 min at 70.0 km/h, 10.0 min at 95 km/h, and 30.0 min at 55.0 km/h, and he spends 20.0 min eating lunch and buying gas. What is the average speed for this part of his trip?

Answer 1

Average speed is calculated by dividing the total distance traveled by total time it took him to make the trip. Below are the calculations for total distance and total time.

(1) t = 45 min = 0.75 h ; d = (0.75 h) x (70 km/h) = 52.5 km
(2) t = 10 min = 0.17 h ; d = (0.17 h) x (95 km/h) = 15.83 km
(3) t = 30 min = 0.5 h ; d = (0.5 h) x (55 km/h) = 27.5 km
(4) t = 20 min = 0.33 h ; d = (0.33 h) x (0 km/h) = 0 km

The total distance he traveled is 95.83 km and he traveled for about 1.75 hours. Thus, his average speed is 54.76 km/h.