This method is not unique. If the sixth grade has a good foundation, use arithmetic more, otherwise you might as well.
It is also easy to solve the unknown. In order to make it easier to understand, several schematic diagrams are put in.
(1) railway between the two places1800km; Dragon;
(2)
① As shown in the figure, combined with the original picture, the two cars meet after driving1800km for 5 hours.
∴ ? Sum of the speeds of two vehicles:1800÷ 5 = 360 km/h;
(2) After meeting,
The two cars continued to drive, and the bullet train took 10 hours to reach the station, which is the distance traveled by the high-speed train for 5 hours.
So the speed ratio of high-speed rail and bullet train is 10:5=2: 1,
Therefore, the speed of high-speed rail is 360×2/(2+ 1)=240km/h,
The train speed is 360×1(2+1) =120km/h;
(3)
Look at the original picture first, BC means that the two cars will continue to drive after they meet (of course, the express train will arrive at the station first! )
According to the meaning of the question, in this process, the functional relationship between y and x is:
Y=360x- 1800。 Obviously, this formula only applies to paragraph BC.
That is, after the encounter, the two cars continue to drive until the express train arrives at the station, which is the range of X,
The schematic diagram is as follows:
That is, the five-hour journey of the bullet train and the running time of the high-speed train:
? 120×5÷240=2.5 (hours), (or the ratio from (2): 5÷2)
∴ is BC, y=360x- 1800, where 5 ≤ x ≤ 7.5;
(4) According to the meaning of the question, the bullet train meets the second high-speed train 5.5 hours after the departure.
Method one,
(360×5.5- 1800)÷240=3/4(h)，
Method two,
? Suppose the second high-speed train leaves t hours later than the first high-speed train.
240×(5.5 tons) +5.5× 120= 1800
Solution: x=3/4
Therefore, the second high-speed train leaves 3/4 hours later than the first one.
I hope it helps you!