Question

От причала вниз по реке отплыл плот. Ниже по течению реки на расстоянии 17км от первого причала находится второй причал. От него на встречу плоту через 2/3 ч после отплытия плота отправился теплоход. Собственная скорость теплохода равна25км/ч, а скорость течения реки равна 3км/ч.Через какое время после своего отплытия плот встретится с теплоходом? Изучаемая тема действие с дробями.

Answer 1

Скорость плота=скорость течения
2/3*3=2км проплыл плот в одиночку
17-2=15км было м/у плотом и теплоходом, когда вышел теплоход
3+25-3=25км/ч-скорость сближения
15/25=3/5ч- через столько встретятся после отплытия теплохода
3/5+2/3=9/15+10/15=19/15=1 4/15ч-через столько встретятся после отплытия теплохода
1 4/15ч=1ч 4*60/15мин=1ч 16мин

Answer 2

Problem Analysis

We have a scenario where a raft departs from a dock and travels downstream on a river. A second dock is located 17 km downstream from the first dock. After 2/3 of an hour since the raft's departure, a steamboat sets off from the second dock to meet the raft. The steamboat has a speed of 25 km/h, and the river's current has a speed of 3 km/h. We need to determine how long it will take for the steamboat to meet the raft.

Solution

To solve this problem, we can use the concept of relative speed. The relative speed is the difference between the speeds of two objects moving in opposite directions. In this case, the relative speed between the steamboat and the raft is the sum of their individual speeds.

Let's calculate the relative speed first: - The speed of the steamboat is 25 km/h. - The speed of the river's current is 3 km/h.

Therefore, the relative speed between the steamboat and the raft is 25 km/h + 3 km/h = 28 km/h.

Now, we need to determine the distance that the raft travels before the steamboat starts its journey. Since the raft travels for 2/3 of an hour before the steamboat sets off, we can calculate the distance traveled by the raft using the formula:

Distance = Speed × Time

The speed of the raft is the sum of its own speed and the speed of the river's current, which is 0 km/h + 3 km/h = 3 km/h. The time is 2/3 of an hour.

Let's calculate the distance traveled by the raft: Distance = 3 km/h × (2/3) h = 2 km

Now, we can determine the time it takes for the steamboat to meet the raft. Since the distance between the two docks is 17 km and the raft has already traveled 2 km, the remaining distance that the steamboat needs to cover is 17 km - 2 km = 15 km.

Using the formula:

Time = Distance / Speed

where the distance is 15 km and the speed is the relative speed of 28 km/h, we can calculate the time it takes for the steamboat to meet the raft.

Let's calculate the time: Time = 15 km / 28 km/h ≈ 0.536 hours

Therefore, it will take approximately 0.536 hours for the steamboat to meet the raft after the raft's departure.

Answer

After the raft's departure, it will take approximately 0.536 hours (or about 32.16 minutes) for the steamboat to meet the raft.

Note: The answer is approximate because we rounded the time to two decimal places.