Question

Теплоход прошел по озеру 42 км,а потом проплыл 72 кмпо реке которая впадает в это озеро.Скорость катера 21 км/ч,а скорость течения реки 3 км/ч .Сколько времени нужно теплоходу чтобы вернуться назад?

Answer 1

1)42+72=114(км)                                                                                               2)21+3=24(км/час)                                                                                           3)114:24=4.75(часов)

Answer 2

Calculating the Time Needed for the Return Journey

To calculate the time needed for the return journey, we can use the formula: time = distance / speed.

1. Time to Travel Downstream: - Distance traveled downstream = 72 km (along the river). - Speed of the boat downstream = 21 km/h (boat's speed) + 3 km/h (speed of the river's current) = 24 km/h. - Using the formula, the time taken to travel downstream is: time_downstream = 72 km / 24 km/h = 3 hours.

2. Time to Travel Upstream: - Distance to return upstream = 72 km (back to the lake). - Speed of the boat upstream = 21 km/h (boat's speed) - 3 km/h (speed of the river's current) = 18 km/h. - Using the formula, the time taken to travel upstream is: time_upstream = 72 km / 18 km/h = 4 hours.

3. Total Time for the Return Journey: - The total time needed for the return journey is the sum of the time taken downstream and the time taken upstream: total_time = time_downstream + time_upstream = 3 hours + 4 hours = 7 hours.

Therefore, the time needed for the boat to return back to its starting point is 7 hours.