Question

Два теплохода движутся навстречу друг другу. Собственная скорость теплохода, идущего по течению,-20,8 км/ч, а теплохода, идущего против течения,_19,4 км/ч. Через какое время теплоходы встретятся, если сейчас между ними 140,7 км, а скорость течения- 1,8 км/ч?

Answer 1

19,4-1,8=17,6км/ч скорость против течения

20,8+1,8=22,6км/ч скорость по течению

17,6+22,6=40,2 км/ч общая скорость

140,7/40,2=3,5ч они встретятся

Answer 2

1) 20,8+1,8 = 22,6 (км/час)- скорость теплохода, идущего по течению.

2) 19,4-1,8 = 17,6 (км/час)- скорость теплохода, идущего против.

3) 22,6+17,6 = 40,2 (км/час)- скорость сближения.

4) 140,7:40,2 = 3,5 (часа)- теплоходы встретятся.

3,5 часа  = 3 часа 30 минут

Ответ: через 3 часа 30 минут теплоходы встретятся.

 

Answer 3

Problem Analysis

We are given two boats moving towards each other. The speed of one boat relative to the current is -20.8 km/h, and the speed of the other boat relative to the current is 19.4 km/h. The distance between the boats is 140.7 km, and the speed of the current is 1.8 km/h. We need to find the time it takes for the boats to meet.

Solution

To solve this problem, we can use the formula: time = distance / relative speed.

Let's calculate the relative speed of the boats. The relative speed is the sum of the speeds of the two boats relative to the current: - For the boat going downstream, the relative speed is -20.8 km/h + 1.8 km/h = -19 km/h. - For the boat going upstream, the relative speed is 19.4 km/h + 1.8 km/h = 21.2 km/h.

Now we can calculate the time it takes for the boats to meet: - For the boat going downstream: time = distance / relative speed = 140.7 km / 19 km/h = 7.4 hours. - For the boat going upstream: time = distance / relative speed = 140.7 km / 21.2 km/h = 6.64 hours.

Since the boats are moving towards each other, the time it takes for them to meet is the minimum of the two times calculated above. Therefore, the boats will meet in approximately 6.64 hours.

Answer

The two boats will meet in approximately 6.64 hours.