Question

Sally travels by car from one city to another. She drives for 26.0 min at 83.0 km/h, 52.0 min at 41.0 km/h, and 45.0 min at 60.0 km/h, and she spends 15.0 min eating lunch and buying gas.
What's the average speed (km/h)?
What's the total distance traveled(km)?

Answer 1

The average speed is determined by the following formula:

average speed = [sum of (speed * time for which that speed was traveled)] / total time

average speed = [(83 * 26 + 41 * 52 + 60 * 45 + 0 * 15) / 60] / [(26 + 52 + 45 + 15) / 60]
*note: The division by 60 is to convert minutes to hours. We see that the 60 cancels from the top and bottom of the division

average speed = 50.65 km/hr

The total distance traveled is equivalent to the numerator of the fraction we used in the first part. This is:
Distance = (83 * 26 + 41 * 52 + 60 * 45 + 0 * 15) / 60

Distance = 116.5 kilometers