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The fifth grade mathematics basic training book 1 page 32 answer.
20. Two cars, A and B, drive in opposite directions from two places 325 kilometers apart at the same time. Car A travels 52 kilometers per hour, and the speed of car B is 1.5 times that of car A. When will the cars meet?

Solution: velocity b = 52×1.5 = 78 km/h.

325/(52+78)=325/ 130=2.5.

2 1, two cars, Party A and Party B, start from A and B at the same time and drive in opposite directions. A travels 80 kilometers per hour, and B travels 10% of the whole journey per hour. When B travels to 5/8 of the whole journey, Party A can reach B through 65438+ 0/6 of the whole journey. How many kilometers is it between A and B?

Solution: 5/8 of the whole journey of Bank B = (5/8)/(110) = 25/4 hours.

AB distance = (80× 25/4)/(1-kloc-0//6) = 500× 6/5 = 600 km.

22. Two cars, A and B, leave the two places relatively at the same time. Car A travels 40 kilometers per hour and car B travels 45 kilometers per hour. When the two cars meet, the second car is 20 kilometers away from the midpoint. How many kilometers are the two places apart?

Solution: The speed ratio of A and B = 40: 45 = 8: 9.

Distance ratio between Party A and Party B = 8: 9.

When meeting, Party B made the whole journey of 9/ 17.

Then the distance between the two places = 20/(9/17-1/2) = 20/(1/34) = 680km.

23. Party A and Party B walk in opposite directions in two places at the same time, and meet at E. Party A continues to walk at B. Party B takes a rest 14 minutes, and then continues to walk at A. Party A and Party B turn back immediately after arriving at B and A respectively, and still meet at E. Know that A walks 60 meters per minute, B walks 80 meters per minute, and how many meters are there between A and B.

Solution: treat the whole process as a unit 1.

The speed ratio between Party A and Party B is 60: 80 = 3: 4.

The distance a of point E is 3/7 of the whole journey.

When we meet for the second time, one * * * is three times.

After resting 14 minutes, A walked 60× 14=840 meters.

After the first meeting, B left 3/7×2=6/7.

Then the distance traveled by A is 6/7×3/4=9/ 14.

In fact, A left 4/7×2=8/7.

Then during B's rest, A left 8/7-9/ 14= 1/2.

Then the whole journey = 840/( 1/2) = 1680m.

24. Two trains, A and B, leave relatively from AB at the same time. When they meet, the distance ratio between A and B is 4: 5. It is known that train B travels 72 kilometers per hour, and it takes 10 hour for train A to complete the whole journey. How many kilometers are there between AB and AB?

Solution: The ratio of the distance left when meeting is 4: 5.

Then the distance ratio is 5: 4.

The time ratio is equal to the inverse ratio of the distance ratio.

Distance ratio between Party A and Party B = 5: 4.

The time ratio is 4: 5.

Then it takes 10×5/4 = 12.5 hours for line B to complete the journey.

Then AB distance =72× 12.5=900 km.

25. Party A and Party B walk from A and B to each other at the speed of 4 kilometers and 5 kilometers per hour respectively. After meeting, they walked on. How many kilometers is there between A and B if A walks from the assembly point for another two hours and arrives at B?

Solution: The distance ratio when A and B meet = the speed ratio = 4: 5.

Then when they meet, A is 5/9 of the distance from the destination.

So AB distance = 4× 2/(5/9) = 72/5 = 14.4km.