Question

Два велосипедиста отправились из одного посёлка одновременно в противоположных направлениях .Через 30 минут расстояние между ними было 15 км.Средняя скорость одного из них 260 м/мин .Узнай среднюю скорость другого велосипедиста .(Выразите 15 км в метрах.) Составь и реши две обратные задачи. Помогите, очень срочно!!!

Answer 1

Скорость первого - 260 м/мин
Скорость второго - ? м/мин
Расстояние 15 км = 15000 м
Время 30 мин
1) 260 * 30 = 7800 (м)
2) 15000 - 7800 = 7200 (м)
3) 7200 : 30 = 240 (м/мин) - скорость второго

Answer 2

Problem Analysis

We have two cyclists who start from the same village at the same time and travel in opposite directions. After 30 minutes, the distance between them is 15 km. We are given the average speed of one cyclist as 260 m/min. We need to find the average speed of the other cyclist.

Solution

Let's assume the average speed of the second cyclist is x m/min.

We know that the distance covered by the first cyclist in 30 minutes is 260 m/min * 30 min = 7800 m.

Similarly, the distance covered by the second cyclist in 30 minutes is x m/min * 30 min = 30x m.

Since the total distance between them after 30 minutes is 15 km = 15000 m, we can write the equation:

7800 m + 30x m = 15000 m

Now, let's solve this equation to find the value of x.

7800 m + 30x m = 15000 m

Subtracting 7800 m from both sides:

30x m = 7200 m

Dividing both sides by 30:

x m = 240 m/min

Therefore, the average speed of the second cyclist is 240 m/min.

Reverse Problem 1: Finding the Distance

Let's say the average speed of the second cyclist is 240 m/min. We want to find the distance between the two cyclists after 30 minutes.

We know that the distance covered by the first cyclist in 30 minutes is 7800 m.

The distance covered by the second cyclist in 30 minutes is 240 m/min * 30 min = 7200 m.

Therefore, the total distance between them after 30 minutes is 7800 m + 7200 m = 15000 m.

Reverse Problem 2: Finding the Time

Let's say the average speed of the second cyclist is 240 m/min. We want to find the time it takes for the distance between the two cyclists to be 15 km.

We know that the distance covered by the first cyclist in 30 minutes is 7800 m.

The distance covered by the second cyclist in t minutes is 240 m/min * t min = 240t m.

Therefore, the total distance between them after t minutes is 7800 m + 240t m.

We want this total distance to be 15 km = 15000 m.

7800 m + 240t m = 15000 m

Subtracting 7800 m from both sides:

240t m = 7200 m

Dividing both sides by 240:

t min = 30 min

Therefore, it will take 30 minutes for the distance between the two cyclists to be 15 km.

I hope this helps! Let me know if you have any further questions.