Question

Пункты А, Б, С расположены на реке в указанном порядке вниз по течению. Расстояние между А и Б равно 4 км, а между Б и С - 14 км. В 12 часов из пункта Б отплыла лодка и направилась в пункт А. Достигнув пункта А, она сразу же повернула назад и в 14 часов прибыла в пункт С. Скорость течения - 5 км/ч. Найти скорость лодки в стоячей воде.

Answer 1

решение в прикрепленном файле

Answer 2

Problem Analysis

We are given three points, A, B, and C, located on a river in the order of downstream flow. The distance between A and B is 4 km, and the distance between B and C is 14 km. A boat departs from point B at 12:00 and heads towards point A. After reaching point A, it immediately turns back and arrives at point C at 14:00. The speed of the river current is 5 km/h. We need to find the speed of the boat in still water.

Solution

Let's assume the speed of the boat in still water is x km/h.

When the boat is traveling from B to A, it is moving against the current, so its effective speed is (x - 5) km/h. The distance between B and A is 4 km, and the time taken to cover this distance is 2 hours (from 12:00 to 14:00).

Using the formula speed = distance / time, we can write the equation: (x - 5) = 4 / 2

Simplifying the equation, we get: (x - 5) = 2

Solving for x, we find: x = 7

Therefore, the speed of the boat in still water is 7 km/h.

Answer

The speed of the boat in still water is 7 km/h.