Question

Karina travels 70 miles at an average speed of 50 mph.

She then travels a further 60 miles.
The average speed for the entire journey is 44 mph.
Assuming Karina didn't stop, what was her average speed for the final 60 miles to 2 dp?​

Answer 1

38.60 mph

Explanation:

Average speed = total distance / total time

44 mph = (70 mi + 60 mi) / t

t = 2.95 hr

The time spent during the first 70 miles is:

d = rt

70 mi = (50 mph) t

t = 1.4 hr

So the time spent during the last 60 miles is:

t = 2.95 hr − 1.4 hr

t = 1.55 hr

So the average speed during the last 60 miles is:

d = rt

60 mi = r (1.55 hr)

r = 38.60 mph