Question

a car traveled twice as fast on a dry road as it did making the return on a slippery road. the trip was 60 mi each way, and the round trip took 35 hr. what was the speed of the car on the dry road?

Answer 1

the time it takes is distance / speed for each way.
so, the total time is:
dry time + wet time = distance/dry speed + distance/wet speed
and we also know that dry speed = wet speed * 2
so we can replace the terms we know in the previous equation.

total time = 60/(2* wet speed) + 60/wet speed = 30/wet speed + 60/wet speed = 35
90/wet speed = 35
wet speed = 90/35 = 45/7 = 6.4 mi/hr so dry speed is twice that at 12.8