Question

Скорость катера в стоячей воде 15км/ч.на путь от пристани А до пристани В по течению реки он тратит 3ч,а на обратный путь 4,5 ч.какова скорось течения реки? 35 БАЛЛОВ!!!

Answer 1

Решение задания смотри на фотографии

Answer 2

Calculation of River Current Speed

To determine the speed of the river current, we can use the information provided about the time it takes for the boat to travel from point A to point B and back. Let's denote the speed of the boat in still water as x km/h and the speed of the river current as y km/h.

Given: - Speed of the boat in still water: 15 km/h - Time taken from point A to point B (with the current): 3 hours - Time taken from point B to point A (against the current): 4.5 hours

To calculate the speed of the river current, we can set up the following equations:

1. When traveling with the current: - Speed of the boat + Speed of the current = Speed of the boat relative to the ground - 15 + y = (distance AB) / 3 2. When traveling against the current: - Speed of the boat - Speed of the current = Speed of the boat relative to the ground - 15 - y = (distance BA) / 4.5 We can solve this system of equations to find the speed of the river current.

Solving the Equations

Let's solve the system of equations using the substitution method:

From equation 1, we can express the distance AB in terms of the boat's speed and the current speed: - Distance AB = (15 + y) * 3

Substituting this expression into equation 2, we get: - 15 - y = [(15 + y) * 3] / 4.5

Simplifying the equation: - 15 - y = (45 + 3y) / 4.5

Multiplying both sides of the equation by 4.5 to eliminate the denominator: - 67.5 - 4.5y = 45 + 3y

Combining like terms: - 7.5y = 22.5

Dividing both sides of the equation by 7.5: - y = 3

Answer

The speed of the river current is 3 km/h.