Question

Из пункта А отправили по течению реки плот. Через 5 часов 20 минут вслед за ним вышла из пункта А моторная лодка, которая догнала плот на расстоянии 20 км от А .С какой скоростью двигался плот, если известно, что моторная лодка шла быстрее его на 12 км/ч.

Answer 1

Хкм/ч-скорость плота,х+12км/ч-скорость лодки
20/х-20/(х+12)=16/3
16х²+192х-60(х+12-х)=0
16х²+192х-720=0
х²+12х-45=0
х1+х2=-12 и х1*х2=-45
х1=-15 не удов усл
х2=3км/ч-скорость плота

Answer 2

Problem Analysis

We are given that a raft was sent downstream from point A, and after 5 hours and 20 minutes, a motorboat left point A and caught up with the raft at a distance of 20 km from point A. We need to determine the speed of the raft, given that the motorboat was traveling 12 km/h faster than the raft.

Solution

Let's assume the speed of the raft is x km/h. Since the motorboat was traveling 12 km/h faster, its speed would be x + 12 km/h.

We know that the time taken by the motorboat to catch up with the raft is 5 hours and 20 minutes, which is equivalent to 5.33 hours.

To find the speed of the raft, we can use the formula: speed = distance / time.

The distance covered by the motorboat is the same as the distance covered by the raft, which is 20 km.

Substituting the values into the formula, we have:

x = 20 km / 5.33 hours

Now, let's calculate the speed of the raft.

Calculation

Using the formula speed = distance / time, we can calculate the speed of the raft:

x = 20 km / 5.33 hours

Calculating the value of x:

x ≈ 3.75 km/h

Therefore, the speed of the raft is approximately 3.75 km/h.

Answer

The raft was moving at a speed of approximately 3.75 km/h.