Question

When you enter the Texas Turnpike, they give you a ticket showing the time and place of your entry. When you exit, you turn in this ticket and they use it to figure your toll. Because they know the distance between toll stations, they can also use it to check your average speed against the turnpike limit of 65 mph. On your trip, heavy snow limits your speed to 40 mph for the first 120 mi. At what average speed can you drive for the remaining 300 mi without having your ticket prove that you broke the speed limit?

Answer 1

87 mph

Explanation:

Total distance needed is 120 mi + 300 mi and that is 420 mi.

Driving at 65 mph means that it would take

420 / 65 hours to reach his destination.

6.46 hours .

at the first phase, he drove at 40 mph for 120 mi, this means that it took him

120 / 40 hours to complete the journey.

3 hours.

the total time needed for the whole journey is 6.46 hours, and he already spent 3 hours in the first phase. To keep up with the 6.46 hours required, in the second phase, he has to drive at a speed of

6.46 - 3 hours = 3.46 hours.

300 mi / 3.46 hours => 86.71 mph approximately 87 mph

Therefore, he needs to drive at not more than 87 mph to keep up with the journey while not breaking his speed limit