Question

Два поезда движутся навстречу друг другу по параллельным путям,первый-со скоростью 70км/ч,второй-со скоростью 50км/ч.Пассажир ,сидящий во втором поезде,заметил ,что первый поезд шел мимо него 9с.Какова длина первого поезда?

Answer 1

1) 70+50=120 км/ч - скорость встречного поезда относительно пассажира.
2) 120 км/ч= 120*1000/60= 2000 м/мин
3) 9 сек=0,15 минут
4) 2000*0,15=300 метров длина поезда

Answer 2

Problem Analysis

We have two trains moving towards each other on parallel tracks. The first train is traveling at a speed of 70 km/h, and the second train is traveling at a speed of 50 km/h. The passenger in the second train notices that the first train passes by in 9 seconds. We need to find the length of the first train.

Solution

To find the length of the first train, we can use the formula:

Length = Speed × Time

Let's calculate the length of the first train using this formula.

Calculation

Given: - Speed of the first train = 70 km/h - Speed of the second train = 50 km/h - Time taken for the first train to pass by the passenger in the second train = 9 seconds

Using the formula, we can calculate the length of the first train:

Length = Speed × Time

For the first train: Length = 70 km/h × 9 s

To calculate the length, we need to convert the speed from km/h to m/s, as the time is given in seconds.

Converting the speed from km/h to m/s: 70 km/h = (70 × 1000) m/ (60 × 60) s = 19.44 m/s

Now, we can calculate the length of the first train: Length = 19.44 m/s × 9 s

Calculating the length: Length = 175.56 m

Answer

The length of the first train is 175.56 meters.

Explanation

When two trains are moving towards each other on parallel tracks, the relative speed between them is the sum of their individual speeds. In this case, the relative speed is 70 km/h + 50 km/h = 120 km/h. The first train passes by the passenger in the second train in 9 seconds. By multiplying the relative speed by the time, we can find the distance traveled by the first train, which is equal to its length. Therefore, the length of the first train is 175.56 meters.