Speed Time and Distance -1

A boat traveled upstream a distance of 90 miles at an average speed of (v-3) miles per hour and then traveled the same distance downstream at an average speed of (v+3) miles per hour. If the trip upstream took half an hour longer than the trip downstream, how many hours did it take the boat to travel downstream?

A: 2.5
B: 2.4
C: 2.3
D: 2.2
E: 2.1


90/(V-3) = 1/2 + 90/(V+3)
90/(V-3) - 90/(V+3) = 1/2
[90(V+3) - 90(V-3)] / (V+3) (V-3) = 1/2
[90V + 270 - 90V +270] = [V^2 - 9]/2
540 *2 = V^2 - 9
1080 + 9 = V^2
1089 = V^2
V = 3*11 = 33
Downstream = 90/(v+3) = 90/36 = 10/4 = 2.5