Question

Туристы проплыли на лодке по озеру 15 км за такое же время, что и 18 км по течению реки. Найдите скорость лодки по озеру, если скорость течения реки 2 км/ч

Answer 1

Пусть скорость лодки по озеру х, тогда по реке - х+2
по условию
18:(х+2)=15:х
18х=15х+30
3х=30
х=10 км/ч
можно сделать проверку
Ответ: 10 км/час

Answer 2

Problem Analysis

We are given that tourists traveled 15 km on a lake in the same amount of time it took them to travel 18 km downstream on a river. We need to find the speed of the boat on the lake, given that the speed of the river's current is 2 km/h.

Solution

Let's assume the speed of the boat on the lake is x km/h.

The time taken to travel a certain distance is given by the formula: time = distance / speed.

For the lake journey, the time taken is the same as the time taken for the river journey. Therefore, we can set up the following equation:

15 / x = 18 / (x + 2)

To solve for x, we can cross-multiply and solve the resulting equation.

Calculation

Cross-multiplying the equation, we get:

15 * (x + 2) = 18 * x

Expanding the equation:

15x + 30 = 18x

Subtracting 15x from both sides:

30 = 3x

Dividing both sides by 3:

x = 10

Answer

The speed of the boat on the lake is 10 km/h.

Please let me know if I can help you with anything else.