Question

моторная лодка ,скорость которой в стоячей воде 15км/ч, прошла по течению реки 35 км, а против течения 25км.На путь по течению она затратила столько же времени ,что и на путь против течения .Какова скорость течения реки?

Answer 1

х км/ч скорость течения

(15-х) скорость против течения

(15+х)скорость по течению

Время одинаковое

35:(15+х)=25:(15-х)

525-25х=375+25

60х=150

х=2,5 км/ч

Answer 2

Calculation of River Current Speed

To calculate the speed of the river current, we can use the information provided. Let's break down the given information:

- The speed of the motorboat in still water is 15 km/h. - The motorboat traveled 35 km downstream (with the current). - The motorboat traveled 25 km upstream (against the current). - The time taken to travel downstream is the same as the time taken to travel upstream.

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

Speed of the river current = (Speed downstream - Speed upstream) / 2

Let's substitute the given values into the formula:

Speed of the river current = (15 km/h - Speed upstream) / 2

Now, we need to find the speed upstream. Since the time taken to travel downstream is the same as the time taken to travel upstream, we can use the formula:

Time = Distance / Speed

Let's calculate the time taken to travel downstream and upstream:

Time downstream = Distance downstream / Speed downstream = 35 km / 15 km/h

Time upstream = Distance upstream / Speed upstream = 25 km / Speed upstream

Since the time taken is the same, we can equate the two equations:

35 km / 15 km/h = 25 km / Speed upstream

Now, let's solve for the speed upstream:

Speed upstream = (25 km / Speed upstream) * (15 km/h / 35 km)

Simplifying the equation:

Speed upstream = (25 * 15) / (35)

Calculating the value:

Speed upstream = 10.714 km/h

Now, let's substitute the value of the speed upstream into the formula for the speed of the river current:

Speed of the river current = (15 km/h - 10.714 km/h) / 2

Calculating the value:

Speed of the river current = 2.643 km/h

Therefore, the speed of the river current is approximately 2.643 km/h.