The motor ship covered 192 km against the river in 8 hours. How much time to spend on the return trip if the river speed is 4 km / h.

Let us denote the speed of the motor ship through x. The speed of the river must be taken into account. Since the motor ship was moving against the current, its speed will be equal to x – 4. Let’s find the speed of the motor ship by the formula S = t * v, where S is the distance traveled, t is time, v is the speed.
8 * (x – 4) = 192
Find the value of x.
x – 4 = 192/8
x – 4 = 24
x = 28 km per hour.
Let’s determine the time spent by the ship on the return journey. Since it moves with the current, we add the speed of the river to the speed of the motor ship.
192 = t * (28 + 4)
t = 192/32
t = 6 hours.
Answer: the ship will spend 6 hours on the way back.