Question

Из одного города в одном направлении вышли 2 поезда. Скорость первого поезда 60 км/ч, а второго - 90 км/ч, и он вышел на 2 ч позже. Через сколько часов после отправления второй поезд поравняется с первым?

Answer 1

60*2=120 км прошёл первый
90-60=30 км/ч скорость сближения
120:30=4 ч
ответ: через 4ч

Answer 2

Problem Analysis

Two trains are traveling in the same direction. The first train has a speed of 60 km/h, and the second train has a speed of 90 km/h. The second train departs 2 hours later than the first train. We need to find out after how many hours the second train will catch up to the first train.

Solution

Let's denote the time it takes for the second train to catch up to the first train as t hours.

The distance traveled by the first train when the second train starts is 60t km.

The distance traveled by the second train when it catches up to the first train is 90(t-2) km.

Setting these distances equal to each other, we can solve for t.

Calculation

Setting up the equation: 60t = 90(t-2)

Solving for t: 60t = 90t - 180 30t = 180 t = 6

Answer

The second train will catch up to the first train after 6 hours.