Question

Срочно! Пожалуйста кр. Лодка собственная скорость которой 7 км/ч шла по течения 18 км; против течения 15 км, лодка находилась на воде 5 часов .Найти скорость течения реки

Answer 1

Скорость по течению =7+х
Скорость против течения=7-х
Время по течению=18/7+х
Время против течения=15/7-х
По идее: 18/7+х + 15/7-х=5
Но у меня в уравнении получилось 75,...
скорость течения не может быть столько

Answer 2

Calculation of River Current Speed

To find the speed of the river current, we can use the formula:

Speed of boat in still water = Speed of boat downstream = Speed of boat upstream

Let's denote the speed of the boat in still water as x and the speed of the river current as y.

Given information: - Speed of the boat in still water (own speed): 7 km/h - Time taken to travel downstream (with the current): 18 km - Time taken to travel upstream (against the current): 15 km - Total time spent on the water: 5 hours

Using the formula, we can set up the following equations:

1. Downstream: (x + y) * 18 = 5 2. Upstream: (x - y) * 15 = 5

To solve this system of equations, we can use substitution or elimination method. Let's use the substitution method.

From equation 1, we can express x in terms of y: x = 5/18 - y

Substituting this value of x into equation 2, we get: (5/18 - y - y) * 15 = 5

Simplifying the equation: (5/18 - 2y) * 15 = 5 75/18 - 30y = 5 75 - 30y = 90 -30y = 15 y = -15/30 y = -0.5 km/h

Therefore, the speed of the river current is 0.5 km/h.

Please note that the negative sign indicates that the current is flowing in the opposite direction of the boat's motion.