In the first semester of the first semester of junior high school, we can use equation or not, but there must be process A and B ride bicycles on the road parallel to the railway. They ride 15 kilometers per hour. Now there is a train coming. It takes 30 seconds for the train to pass by a and 20 seconds for the train to pass by B. the speed of the train is calculated

In the first semester of the first semester of junior high school, we can use equation or not, but there must be process A and B ride bicycles on the road parallel to the railway. They ride 15 kilometers per hour. Now there is a train coming. It takes 30 seconds for the train to pass by a and 20 seconds for the train to pass by B. the speed of the train is calculated

The mathematical method is simple. Let the train length be x and the train speed be y
X / (Y-15) = 30 and X / (y + 15) = 20
The result is y = 75, which is what you want

A and B bicycles, on the road parallel to the railway, travel 15 kilometers per hour. There is a train coming. It takes 30 seconds for the train to pass a bicycle and 20 seconds for the train to pass B bicycle. The speed of the train is calculated

15 km / h = 416 M / s. assuming the train speed is x m / s, the equation can be obtained as follows: (416 + x) × 20 = (x-416) × 30 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 8313x + 20x = 30x-125, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 10x = 20813, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 2056. A: the train speed is 2056 M / s

A and B bicycles, on the road parallel to the railway, travel 15 kilometers per hour. There is a train coming. It takes 30 seconds for the train to pass a bicycle and 20 seconds for the train to pass B bicycle. The speed of the train is calculated

15 km / h = 416 M / s, assuming that the speed of the train is x m / s, the equation can be obtained as follows: (416 + x) × 20 = (x-416) × 30 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 8313x + 20x = 30x-125, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 10x = 20813, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp