The motor ship travels a certain distance along the river in 10 hours, and against the current in 20 hours
The motor ship travels a certain distance along the river in 10 hours, and against the current in 20 hours. How long does it take for a chip thrown into the river to travel this distance?
Let’s designate the conditional distance that the motor ship travels as 1.
Let’s find its speed along the river.
We divide the distance by time.
1/10 = 1/10 part of the way per hour.
Determine the speed of the ship against the flow of the river.
1/20 = 1/20 part of the way per hour.
We find the difference in speed of the ship along the river and against it.
1/10 – 1/20 = 2/20 – 1/20 = 1/20.
Determine the speed of the river.
We divide the speed difference into 2 parts.
1/20 / 2 = 1/20 * 1/2 = 1/40.
So the chip will go this way for:
1 / 1/40 = 1 * 40/1 = 40 hours.
Answer:
40 h.