Question

Мальчик уронил в речку мяч и обнаружил это через 20 минут, отправился его догонять. Какое расстояние проплывет мальчик пока не догонит мяч, если скорость течения реки 3 км, а собственная скорость плавания мальчика 5 км/с?

Answer 1

3*1/3=1км проплыл мяч за 1/3часа это расстояние между мячом и мальчиком
5+3=8км/в час скорость плавания мальчика по течению
5-3=2км/в час скорость приблежения мальчика к мячу
расстояние :скорость=время
1:2=0,5(час)мальчик догонит мяч за 0,5ч
скорость мальчика 5км/час
5*0,5=2,5км/часпроплывёт мальчик пока не догонит мяч

Answer 2

Problem Analysis

A boy dropped a ball into a river and noticed it 20 minutes later. He then went to catch up with the ball. We need to calculate the distance the boy will swim before catching up with the ball. We are given that the river's current speed is 3 km/h, and the boy's swimming speed is 5 km/h.

Calculation

To calculate the distance the boy will swim before catching up with the ball, we need to determine the time it takes for the boy to catch up with the ball.

Let's assume the distance the boy swims is D km, and the time it takes for the boy to catch up with the ball is T hours.

The time it takes for the ball to travel downstream (with the current) is 20 minutes, which is equal to 1/3 of an hour. Therefore, the distance the ball travels downstream is:

Distance downstream = (River's current speed) x (Time) = 3 km/h x 1/3 h = 1 km

Since the boy swims at a speed of 5 km/h, the time it takes for the boy to catch up with the ball is:

T = (Distance downstream) / (Boy's swimming speed) = 1 km / 5 km/h = 1/5 h = 12 minutes

Therefore, the boy will catch up with the ball after swimming for 12 minutes.

To calculate the distance the boy will swim before catching up with the ball, we can use the formula:

Distance = (Boy's swimming speed) x (Time) = 5 km/h x 1/5 h = 1 km

Therefore, the boy will swim a distance of 1 kilometer before catching up with the ball.

Answer

The boy will swim a distance of 1 kilometer before catching up with the ball.