Question

Расстояние между пристанями А и В равно 145 км Из пристани А вниз по течению отправили плот. Из пристани В, навстречу с плотом, отплыла моторная лодка. Собственная скорость лодки 29 км/ч. Через какое время встретились плот и моторная лодка (в часах), если скорость течения реки равна 2 км/ч?

Answer 1

Ответ: 5 часов

Пошаговое объяснение:

           Плот                                               Лодка

1час       2км                                                 27км

2часа     4км                                                 54км    

3часа      6км                                                81км

4часа      8км                                                 108км

5часв       10км                                              135км

135+10=145(все расстояние)

плот имеет скорость течения а тоисть 2 км

а лодка каждый час проезжает 29км/час-2км/час течение которое течет ему напротив,

Answer 2

Problem Analysis

We are given that the distance between two docks, A and B, is 145 km. A raft is sent downstream from dock A, while a motorboat departs from dock B towards the raft. The motorboat has a speed of 29 km/h, and the river's current is flowing at a speed of 2 km/h. We need to determine the time it takes for the raft and the motorboat to meet.

Solution

To solve this problem, we can use the concept of relative speed. The relative speed is the difference between the speeds of two objects moving in opposite directions.

Let's assume that the time it takes for the raft and the motorboat to meet is 't' hours. During this time, the raft will travel downstream for 't' hours, covering a distance of (t * (29 + 2)) km. The motorboat will travel upstream for 't' hours, covering a distance of (t * (29 - 2)) km.

Since the total distance between the docks is 145 km, we can set up the following equation:

(t * (29 + 2)) + (t * (29 - 2)) = 145

Simplifying the equation:

(31t) + (27t) = 145

58t = 145

t = 145 / 58

t ≈ 2.5 hours

Therefore, it will take approximately 2.5 hours for the raft and the motorboat to meet.

Answer

The raft and the motorboat will meet after approximately 2.5 hours.

Explanation

During this time, the raft will travel downstream for 2.5 hours, covering a distance of (2.5 * (29 + 2)) km = 77.5 km. The motorboat will travel upstream for 2.5 hours, covering a distance of (2.5 * (29 - 2)) km = 67.5 km. The sum of these distances is equal to the total distance between the docks, which is 145 km.