Question:
An ordinary cyclist travels up and down a hill. Going up, she maintains a constant speed of 10 mph. It takes her 1 hour to get to the top. Assuming that the hill is symmetric, what speed must she maintain on the way going down if she wishes to average 20 mph?

Option A):
10
Option B):
60
Option C):
20
Option D):
None

Correct Answer is Option D):
None