Final answer:
The car travels at 50 miles per hour on level ground. To travel 30 miles at this speed takes 0.6 hours, or 36 minutes, which is closest to 1 hour from the given options.
Step-by-step explanation:
To determine how long it will take the car to travel 30 miles on level ground, first we need to understand the car's speed on level ground given the conditions described. According to the problem, the car travels four times as fast downhill as it does uphill and twice as fast on level ground as it does uphill. If the car travels 100 miles per hour downhill, it would travel 25 miles per hour uphill (100 mph divided by 4) and 50 miles per hour on level ground (25 mph multiplied by 2).
Knowing that the car's speed on level ground is 50 mph, we can calculate the time it takes to travel 30 miles by dividing the distance by speed. The time (t) required to travel 30 miles on level ground at a speed of 50 miles per hour is given by:
t = distance/speed = 30 miles / 50 miles per hour = 0.6 hours
0.6 hours is the same as 36 minutes, which is less than 1 hour and does not match any of the multiple-choice answers precisely. However, if we must choose the closest answer from the options provided, 0.6 hours is closest to:
B) 1 hour