The "encounter problem" (or the opposite problem) is that two objects start from two places at different speeds at the same time, (
Or walk away from a place at the same time), after several hours of meetings (
Or separate). If we call the sum of the speeds of two objects "the sum of the speeds", from starting at the same time to meeting (
Or distance), this period of time is called "meeting time"; The distance that two objects walk at the same time is called "meeting distance", so their relationship is:
Speed sum × meeting time = meeting distance
Meeting distance/speed sum = meeting time
Meet distance ÷ meet time = speed and.
1, two cars, A and B, leave from A and B relatively simultaneously. Car A travels 42.5 kilometers per hour and car B travels 38 kilometers per hour. Four hours later, the distance between the two cars is still 35.
5 kilometers, find the distance between A and B?
Analysis:
From the question, we know the speed of car A and car B, and the sum of their speeds is 42.5+38 = 80.5 (km).
The meeting time is 4 hours, and the meeting distance is ok.
The distance between A and B is: the distance of meeting+the distance of 35.5 kilometers.
Solution: (42.5+38) × 4+35.5
=80.5×4+35.5
=322+35.5
= 357.5 km
A: The distance between A and B is 357.5 kilometers.
2. A truck and a bus drive in opposite directions from two places 299 kilometers apart at the same time. Trucks travel 40 kilometers per hour and buses travel 52 kilometers per hour. Q: How many hours later, the distance between the two cars was 69 kilometers for the first time? How long before the distance between the two cars is 69 kilometers again?
Analysis:
As can be seen from the meaning of the question, the first distance is 69 kilometers, that is, the two cars have not met yet, and they are still 69 kilometers away. The meeting distance should be 299-69.
According to the sum of meeting distance and speed = meeting time, that is, 230-(40+52) = 2.5 (hours).
The second time was 69 kilometers apart, after the first meeting was 69 kilometers apart, and later it was 69 kilometers apart. Actually, there are two rows of 69 kilometers.
According to: the sum of distance and velocity = time, it can be solved.
Solution: (299-69) ÷ (40+52)
=230÷92
= 2.5 hours
( 69×2 )÷( 40+52 )
= 138÷92
= 1.5 (hours)
A: After 2.5 hours, the distance between the two cars was 69 kilometers for the first time, 1.5 hours later, the distance between the two cars was 69 kilometers again.
It should be detailed enough! I hope it helps you!