Question

Лодка первую четверть пути плывет со скоростью 15 м\с а остальные 180 м проходит за 20 с найдите среднюю скорость лодки на всем пути

Answer 1

180/20 равно 9
15+9/2равно 12

Answer 2

180/20=9 (м/с) - скорость лодки на оставшийся путь 
(15+9)/2=12 (м/с) - средняя скорость лодки

Answer 3

Problem Analysis

We are given that a boat travels the first quarter of its journey at a speed of 15 m/s, and the remaining 180 m is covered in 20 seconds. We need to find the average speed of the boat for the entire journey.

Solution

To find the average speed, we can use the formula:

Average Speed = Total Distance / Total Time

Let's calculate the total distance and total time for the boat's journey.

The boat travels the first quarter of its journey at a speed of 15 m/s. Let's assume the total distance of the journey is D.

The distance covered in the first quarter of the journey is D/4, and the time taken is (D/4) / 15.

The remaining distance covered is 180 m, and the time taken is 20 seconds.

The total distance is D, and the total time is (D/4) / 15 + 20.

Now we can substitute these values into the formula to find the average speed.

Average Speed = D / [(D/4) / 15 + 20]

Let's simplify this equation to find the average speed.

Calculation

To simplify the equation, we can multiply both the numerator and denominator by the denominator's reciprocal.

Average Speed = D * [15 + 20 * (4/D)]

Simplifying further:

Average Speed = 15D + 80

Therefore, the average speed of the boat for the entire journey is 15D + 80 m/s.

Answer

The average speed of the boat for the entire journey is 15D + 80 m/s.

Note: The value of D is not provided in the question, so we cannot calculate the exact average speed without knowing the total distance of the journey.