Question

A motor boat heads upstream a distance of 24 km in a river whose current is running at 3
km per hour. The trip up and back takes 6 hours. Assuming that the motor boat maintained
a constant speed, what was its speed in still water?​

Answer 1

Answer:

9 km/h

Step-by-step explanation:

let the speed in still water = u km/h

24 ÷( u + 3) + 24 ÷ (u-3 ) = 6

4 ÷( u + 3) + 4 ÷ (u-3 ) = 1

8u = u² - 9

u² -8u- 9=0

( u+1 )  ( u-9 ) = 0

u = 9 km/h