Question

туристы взяли на прокат лодку.за 3 ч они поднялись вверх по реке на 12 км и вернулись обратно. какова скорость лодки в стоячей воде если скорость течения 2 км/ч

Answer 1

12/(x+2)+12/(x-2)=3

8x=x^2-4

x^2-8x-4=0

x=4+2sqrt(5)

странное значение, но факт, может ошибка в условии

 

Answer 2

Calculating the Boat's Speed in Still Water

To calculate the speed of the boat in still water, we can use the concept of relative speed. The speed of the boat in still water can be represented as the average speed of the boat during the entire journey.

Given: - Time taken to go up the river and return = 3 hours - Distance traveled up the river = 12 km - Speed of the river's current = 2 km/h

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

The speed of the boat while traveling upstream (against the current) can be represented as (B - C), and the speed of the boat while traveling downstream (with the current) can be represented as (B + C).

Using the formula: Speed = Distance / Time

We can set up the following equations:

1. Upstream speed = Distance / Time = 12 km / 3 hours = 4 km/h 2. Downstream speed = Distance / Time = 12 km / 3 hours = 4 km/h

Now, we can solve for the boat's speed in still water using these equations.

Solving for the Boat's Speed in Still Water

To find the boat's speed in still water, we can use the following equations:

1. Upstream speed = Boat's speed in still water - Speed of the river's current - (B - C) = 4 km/h

2. Downstream speed = Boat's speed in still water + Speed of the river's current - (B + C) = 4 km/h

Adding the two equations together, we get: (B - C) + (B + C) = 4 km/h + 4 km/h 2B = 8 km/h B = 4 km/h

Conclusion

The speed of the boat in still water is 4 km/h.