Question

СРОЧНО! ПРОШУ! Расстояние между двумя пристанями равно 71,4 км. Из них одновременно навстречу друг другу вышли две лодки, скорости которых в стоячей воде равны. Через 1,7 ч. лодки встретились. Скорость течения реки равна 2 км/ч. Скорость лодки в стоячей воде равна ... км/ч. Сколько километров до места встречи пройдёт лодка, плывущая по течению? ... км. Сколько километров до места встречи пройдёт лодка, плывущая против течения? ... км.

Answer 1

Ответ:

Пусть скорость лодки в стоячей воде х км /ч, тогда скорость лодки по течению х+2 км/ч, против течения х-2 км/ч. Первая ложка прошла расстояние 1,7*(х+2) а против течения 1,7*(х-2)

составим уравнение

1,7*(х+2)+1,7*(х-2)=71,4

1,7х+3,4+1,7х-3,4=71,4

3,4х=71,4

х= 71,4/3,4

х=21

Скорость лодки в стоячей воде равна

21 км/ч.

Сколько километров до места встречи пройдёт лодка, плывущая по течению?

(21+2)*1,7=39,1 км.

Сколько километров до места встречи пройдёт лодка, плывущая против течения?

(21-2)*1,7=32,3км.

Пошаговое объяснение:

Answer 2

Problem Analysis

We are given that the distance between two piers is 71.4 km. Two boats start simultaneously from each pier and meet after 1.7 hours. The speed of the river current is 2 km/h, and the speed of the boats in still water is unknown. We need to find the distance traveled by the boat moving with the current and against the current.

Solution

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

To find the distance traveled by the boat moving with the current, we can use the formula:

Distance = Speed × Time

The boat moving with the current will have a net speed of (x + 2) km/h (speed of the boat in still water + speed of the current). The time taken is 1.7 hours. Therefore, the distance traveled by the boat moving with the current is:

Distance with current = (x + 2) × 1.7 km To find the distance traveled by the boat moving against the current, we can use the same formula:

Distance = Speed × Time

The boat moving against the current will have a net speed of (x - 2) km/h (speed of the boat in still water - speed of the current). The time taken is 1.7 hours. Therefore, the distance traveled by the boat moving against the current is:

Distance against current = (x - 2) × 1.7 km Now, we can substitute the given distance between the piers (71.4 km) into the equations and solve for x.

Calculation

Let's solve the equations:

1. Distance with current = 71.4 km - (x + 2) × 1.7 = 71.4 - x + 2 = 71.4 / 1.7 - x + 2 = 42 - x = 42 - 2 - x = 40 km/h

2. Distance against current = 71.4 km - (x - 2) × 1.7 = 71.4 - x - 2 = 71.4 / 1.7 - x - 2 = 42 - x = 42 + 2 - x = 44 km/h

Answer

Therefore, the boat moving with the current will travel 68 km before reaching the meeting point, and the boat moving against the current will travel 74 km before reaching the meeting point.

Please let me know if you need any further clarification.