Question

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

Answer 1

15+5=20
35+20=55
250\55=4,54545454545

Answer 2

Problem Analysis

Two motorboats are traveling towards each other on a river. The first boat has a speed of 15 km/h, while the second boat has a speed of 35 km/h. The first boat is moving with the current of the river, which has a speed of 5 km/h. The distance between the two cities is 250 km. We need to determine how many hours it will take for the boats to meet.

Solution

To solve this problem, we can use the formula: time = distance / relative speed.

Let's calculate the relative speed of the two boats. The relative speed is the sum of the speeds of the two boats when they are moving towards each other.

The speed of the first boat is 15 km/h, and the speed of the second boat is 35 km/h. Since the first boat is moving with the current, we need to subtract the speed of the current (5 km/h) from its speed. Therefore, the relative speed of the two boats is:

Relative speed = (Speed of first boat - Speed of current) + Speed of second boat = (15 km/h - 5 km/h) + 35 km/h = 10 km/h + 35 km/h = 45 km/h

Now, we can calculate the time it will take for the boats to meet by dividing the distance between the two cities by the relative speed:

Time = Distance / Relative speed = 250 km / 45 km/h ≈ 5.56 hours

Therefore, it will take approximately 5.56 hours for the boats to meet.

Answer

The two motorboats will meet after approximately 5.56 hours.

Note: The above calculation assumes that the boats maintain a constant speed throughout the journey and that there are no other factors affecting their movement.