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A goes to school on foot at the speed of 4 kilometers per hour, B starts from the same place by bike 4 hours later than a, B travels 12 kilometers per hour, B______ You can catch up with a in an hour
4 × 4 (12-4) = 2 (hours); answer: B can catch up with a in 2 hours
A and B set out for a certain place at the same time. A walked 4 kilometers per hour. After a walked 16 kilometers, B rode a bicycle at the speed of 12 kilometers per hour
A, ask B, how many hours can we catch up with a!
Set X hours to catch up with a
16+4x=12x
8x=16
x=2
It can catch up with a in 2 hours
A rides from a to B at 12 km / h, while B walks from B to a at 4 km / h
A rides from a to B at a speed of 12 km / h, while B walks from B to a at a speed of 4 km / h. B meets a 1.5 hours after departure. After meeting, the two continue to move forward. A returns to a after a half-hour rest when he arrives at B, and asks how many hours after a leaves B to catch up with B
No points! The landlord is too stingy
Let a and B meet at C, the distance BC = 4 × 1.5 = 6km
The time of a from C to B is 6 / 12 = 0.5 hours
The distance of B from C to B in a is 4 × 0.5 = 2km
The distance b walks from a to B is 4 × 0.5 = 2km
So when a starts to chase B from B, the distance between them is 6 + 2 + 2 = 10km
Suppose a leaves B for X hours and catches up with B
12X=4X+10
X = 1.25 hours
In fact, this question is very simple. If you don't understand, please continue to ask me. Remember to add points
Party A and Party B set out from a certain place. After Party B walked for 2 hours, Party A rode a bicycle at a speed of 25 km / h. The idea and process of solving the problem are very important
Party A and Party B set out from a certain place. After Party B walked for 2 hours, Party A followed the same route by bicycle at the speed of 25 km / h. after 45 minutes, Party A exceeded Party B's speed of 7.75 km
Let B speed x km / h
45 minutes = 45 / 60 = 0.75 hours
B walked a total of 2 + 0.75 = 2.75 hours
A walked for 0.75 hours
∴25×0.75-（2+0.75）X=7.75
18.75-2.75X=7.75
2.75X=18.75-7.75
2.75X=11
X=4
The speed of B is 4 km / h
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