Question

Из двух городов по реке одновременно выплыли навстречу друг другу две моторные лодки. Скорость первой лодки 15км/ч, второй лодки 35км/ч. Первая лодка двигалась по течению реки. Скорость течения реки 5км/ч. Через сколько часов лодки встретились, если расстояние между городами 250км?

Answer 1

To find out how long it took for the boats to meet, we can use the concept of relative speed. The relative speed is the sum of the speeds of the two boats when they are moving towards each other.

Let's calculate the relative speed of the two boats:

- The speed of the first boat is 15 km/h. - The speed of the second boat is 35 km/h. - The speed of the river current is 5 km/h.

To calculate the relative speed, we need to subtract the speed of the river current from the speed of each boat:

- Relative speed = (Speed of the first boat - Speed of the river current) + (Speed of the second boat - Speed of the river current) - Relative speed = (15 km/h - 5 km/h) + (35 km/h - 5 km/h) - Relative speed = 10 km/h + 30 km/h - Relative speed = 40 km/h

Now that we have the relative speed, we can calculate the time it took for the boats to meet by dividing the distance between the cities by the relative speed:

- Time = Distance / Relative speed - Time = 250 km / 40 km/h - Time = 6.25 hours

Therefore, the boats met after approximately 6.25 hours.

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