Solution: velocity sum = 60+40 =100 km/h.
There are two situations,
No encounter
Then the required time =(400- 100)/ 100=3 hours.
Met it.
Then the required time =(400+ 100)/ 100=5 hours.
10, A travels 9 kilometers per hour, and B travels 7 kilometers per hour. They walked back to back at the same time in two places 6 kilometers apart, and a few hours later they were separated by 150 kilometers.
Solution: velocity sum = 9+7 =16 km/h.
Then after (150-6)/16 =144/16 = 9 hours, the distance is150 kilometers.
1 1. Two cars A and B are driving in opposite directions at the same time from two places 600 kilometers apart. It is known that car A travels 42 kilometers per hour and car B travels 58 kilometers per hour. How many kilometers did B car travel when they met?
Solution:
Speed sum =42+58= 100 km/h
Meeting time =600/ 100=6 hours.
When they met, B traveled 58×6= 148 km.
or
The speed ratio of car A and car B is 42: 58 = 21:29.
So when we met, B traveled 600×29/(2 1+29)=348 kilometers.
12, the two cars face each other, meet in six hours, and four hours later, the bus arrives, and the truck is 188 kilometers away. How far is the distance between the two places?
Solution: treat the two cars as a whole.
65438+ 0/6 of the whole journey of two cars per hour
4 hour line 1/6×4=2/3
Then the whole journey =188/(1-2/3) =188× 3 = 564 km.
13. The distance between Party A and Party B is 600 kilometers. The bus and truck traveled in opposite directions from two places and met for six hours. As we all know, the speed of a truck is two-thirds that of a bus. What is the speed of the two cars?
Solution: the sum of the speeds of two cars = 600/6 =100 km/h.
Bus speed =100/(1+2/3) =100× 3/5 = 60 km/h.
Freight car speed = 100-60 = 40km/h
14. The rabbit and the kitten walked in opposite directions from A and B, which are 40 kilometers apart, respectively. Four hours later, they met for four kilometers. How long did it take to meet again?
Solution: velocity sum = (40-4)/4 = 9 km/h.
Then it will take 4/9 hours to meet.
15, car a and car b leave from a and b respectively. Car A travels 50 kilometers per hour and car B travels 40 kilometers per hour. Train A is earlier than train B 1 hour. What's the distance between the two places?
When car A reaches the finish line, car B is 40× 1 = 40km away from the finish line.
Car a travels 40 kilometers more than car B.
Then the time for a car to reach the finish line is 40/(50-40) = 4 hours.
Distance between the two places = 40× 5 = 200km.
16. Two cars leave from Party A and Party B at the same time and meet at 4 o'clock. The speed of the local train is three-fifths of that of the express train. When we met, the express train traveled 80 kilometers more than the local train. How far is the distance between the two places?
Solution: The speed ratio of the express train and the local train = 1: 3/5 = 5: 3.
When they met, the express train traveled 5/8 of the whole journey.
The local train covered three-eighths of the whole journey.
Then the whole journey = 80/(5/8-3/8) = 320km.
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