Question

Серёжа стал догонять Колю, когда тот находился от него на расстоянии 840м, и догнал через 6 мин. Найдите скорость Коли, если его скорость была в 2 раза меньше скорости Сережи

Answer 1

x- скорость Сережи, y- скорость Коли

$\left \{ {{6x-6y=840} \atop {x=2y}} \right$

6*(2y)-6y=840

6y=840

y=140 (м/мин)

Answer 2

Problem Analysis

We are given that Sergey is chasing Kolya, and when Kolya is 840 meters away from Sergey, Sergey catches up to him in 6 minutes. We need to find Kolya's speed if his speed is half of Sergey's speed.

Solution

Let's assume Sergey's speed is S and Kolya's speed is K. We are given that Kolya's speed is half of Sergey's speed, so we can write the equation:

K = S/2

We are also given that Sergey catches up to Kolya when Kolya is 840 meters away from him in 6 minutes. We can use the formula:

Distance = Speed × Time

to write the equation:

840 = (S - K) × 6

Substituting the value of K from the first equation, we get:

840 = (S - S/2) × 6

Simplifying the equation:

840 = (2S - S)/2 × 6

840 = S/2 × 6

840 = 3S

Solving for S:

S = 840/3

S = 280

Therefore, Sergey's speed is 280 units. Since Kolya's speed is half of Sergey's speed, Kolya's speed is:

K = S/2 = 280/2 = 140

So, Kolya's speed is 140 units.

Answer

Kolya's speed is 140 units.