Answer:
60 mph
Explanation:
Each way of the trip is 240 miles.
The round trip is 2 × 240 miles = 480 miles
The first half of the trip, 240 miles, was made at a speed of 30 mph.
s = d/t
st = d
t = d/s
t = 240 miles / 30 mph = 8 hours
The first part of the trip took 8 hours.
The entire round trip is 240 miles × 2 = 480 miles
The speed for the entire trip is 40 mph.
480 miles / 40 mph = 12 hours
12 hours - 8 hours = 4 hours
The return trip takes 4 hours.
The return trip is 240 miles.
s = d/t = 240 miles / 4 hours
s = 60 mph
Answer: 60 mph