Answer:
The the rate of the motorboat in still water is 40 km/h; the rate of the current is 10 km/h.
Step-by-step explanation:
Let u be the rate of the motorboat in still water (in kilometers per hour),
let v be the rate of the current.
Then the rate of the motorboat going downstream is u+v km/h,
while its rate going upstream is u-v km/h.
From the other side, the rate of the motorboat going downstream is 150/3=50km/h = 30 km/h.
Thus you have these two equations
u + v = 50 (1) (for the rate downstream), and
u - v = 30 (2) (for the rate upstream).
To solve the system, add equations (1) and (2). You will get
2u = 50 + 30 = 80; hence,
u = 80/2 = 40 km/h.
Then from the equation (1), v = 50 - u = 50 - 40 = 10 km/h.
ANSWER. The the rate of the motorboat in still water is 40 km/h; the rate of the current is 10 km/h.
