The distance between the two marinas is 120 km. How many hours will a motor ship take to sail back

| May 4, 2021 | education

The distance between the two marinas is 120 km. How many hours will a motor ship take to sail back and forth if its speed against the current is 30 km / h and the speed of the current is 5 km / h?

1. Let us find the own speed of the motor ship, if it is known that its speed against the current is 30 km / h, and the speed of the current is 5 km / h:
Own speed = 30 km / h + 5 km / h = 35 km / h.
2. Let us find the time of the ship on the way in one direction downstream by the formula t = S / v, where S is the way, v is the speed, t is the time:
t = 120 / (35 + 5) = 120/40 = 3 hours.
3. Let’s find the time of the ship that it will spend on the return journey, sailing against the current:
t = 120 / (35 – 5) = 120/30 = 4 hours.
4. Let’s find the time that the boat will spend in both directions:
4 hours + 3 hours = 7 hours.
Answer: the ship will take 7 hours to sail in both directions.



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