Question

Из двух городов навстречу друг другу выехали два поезда. Растояние между городами равно 840 км . Встретились они через 7 часов С какой скоростью шел первый поезд, если скорость второго равна 70 км в час?

Answer 1

1) 7х70=490 км- прошел первый поезд за 7 часов.
2) 840-490=350 км- прошел второй поезд за 7 часов
3) 350:7=50 км/ч
Ответ: скорость второго поезда равна 50 км/ч

Answer 2

Problem Analysis

Two trains are traveling towards each other from two different cities. The distance between the cities is 840 km, and they meet after 7 hours. We need to find the speed of the first train, given that the speed of the second train is 70 km/h.

Solution

Let's denote the speed of the first train as x km/h.

The total distance traveled by both trains when they meet is the sum of the distances covered by each train. This can be represented by the equation: 7x + 7*70 = 840

Solving for x will give us the speed of the first train.

Calculation

7x + 7*70 = 840 7x + 490 = 840 7x = 840 - 490 7x = 350 x = 350 / 7 x = 50

Answer

Therefore, the speed of the first train is 50 km/h.