Question

Два брата отправились в путешествие. первый начал двигаться младший брат со скоростью 20 метров в минуту через две минуты в путь отправился старший брат и догнал младшего через 4 минуты. с какой скоростью двигался старший брат если ни он, ни его брат скорости не меняли?

Answer 1

1) 20 * (2 + 4) = 120 (м) - прошёл младший брат за 6 минут;

2) 120 : 4 = 30 (м/мин) - скорость старшего брата.

Проверка: 20 * 6 = 120 м - прошёл младший брат

                  30 * 4 = 120 м - прошёл старший брат

120 - 120 = 0 - старший брат догнал младшего через 4 минуты.

Ответ: старший брат двигался со скоростью 30 м/мин.

Answer 2

Problem Analysis

Two brothers are on a journey. The younger brother starts moving with a speed of 20 meters per minute. After two minutes, the older brother starts and catches up with the younger brother after four minutes. We need to find the speed at which the older brother was moving.

Solution

Let's assume the speed of the older brother is x meters per minute.

The younger brother travels for 2 minutes at a speed of 20 meters per minute. So, the distance covered by the younger brother is 20 * 2 = 40 meters.

The older brother travels for 4 minutes at a speed of x meters per minute. So, the distance covered by the older brother is x * 4 = 4x meters.

Since the older brother catches up with the younger brother, the distance covered by both brothers is the same. Therefore, we can set up the equation:

40 = 4x

To find the value of x, we can solve this equation.

Calculation

Let's solve the equation 40 = 4x to find the value of x.

Dividing both sides of the equation by 4, we get:

x = 40 / 4 = 10 meters per minute

Answer

The older brother was moving at a speed of 10 meters per minute.

Explanation

The younger brother started moving with a speed of 20 meters per minute and traveled for 2 minutes, covering a distance of 40 meters. The older brother started after 2 minutes and caught up with the younger brother after 4 minutes. To catch up with the younger brother, the older brother must have been moving at a speed of 10 meters per minute. This is because the distance covered by both brothers must be the same when they meet.