Kathryn drove her rig 3 hours before dawn and 5 hours after dawn. If her average speed was 4 miles per hour more in the dark and she covered 500 miles altogethe

Question

Steps on how to solve

Answer 1

Let s = speed in the daylight

Let s + 4 = speed in the dark

 

Before dawn: d=rt

d=3(s+4)

After dawn: d=rt

d=5s

 

 3(s+4) + 5s = 500

3s + 12 + 5s = 500

        8s + 12 = 500

                8s = 488

                 s = 61 mph  (daylight speed)

(s+4) = (61+4) = 65 mph (nighttime speed)