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Fourth grade Mathematical Olympiad problem 1: Flowing itinerary exercises and answers (A)

Twelve, the problem of running water (volume A)

Downstream = Ship Speed + Water Speed

Counterflow = Ship Speed-Water Speed

Ship speed = downstream + countercurrent / 2

Water speed = downstream-countercurrent / 2

Speed = distance / time

I. Fill in the blanks

1.The ship travels in a section of a river of 120 kilometers long, and it uses 10 Xiaoming to go up the current, and 6 hours to go down, the water speed is _______, and the ship speed is ________.

2.A boat goes up against the current, with a water speed of 2 kilometers, a boat speed of 32 kilometers, and a ________ kilometers for 4 hours. (Ship speed, water speed is calculated per hour)

3.A boat travels 8 kilometers per hour in still water, and travels 12 kilometers in reverse for 2 hours at a speed of ________.

4. The speed of a ship in still water is 18 kilometers per hour, and the water speed is 2 kilometers per hour. This boat needs 15 hours to travel from A to B to backwater, so the distance between A and B is _______ thousand. Meter.

5.The two docks are 192 kilometers away. It takes 8 hours for a motorboat to travel down the water. It is known that the speed of the water is 4 kilometers per hour, and it takes ________ hours to complete the travel against the water.

6.The two docks are 432 kilometers away, and the steamer will travel 16 hours along the water. The headwater will travel 9 kilometers less per hour than the water, and it will take more ________ hours than the water.

7. River A is a tributary of River B. The speed of water in River A is 3 kilometers per hour, and the speed of water in River B is 2 kilometers. A boat sails along River A for 7 hours and travels 133 kilometers to River B. In the B river, it will sail 84 kilometers against the water, and this boat will travel for _______ hours.

8.A and B ships head up from the port A. The A ship travels 15 kilometers per hour in still water, the B boat travels 12 kilometers per hour, and the water speed is 3 kilometers per hour. The ship just started to leave. When ship A caught up with ship B, it had left port A ______ kilometers.

9. It is known that for the 80 km waterway, it takes 4 hours for boat A to go down and 10 hours for upstream. If boat B takes 5 hours to go downstream, it will take _______ hours for boat B to go upstream.

10. It is known that 60 kilometers from the place A in the river to Haikou, if the boat goes down the river, it can reach Haikou in 4 hours. The water speed is known to be 6 kilometers per hour. The water speed from the sea to the river is 3 kilometers per hour.It will take another ______ hours for the ship to return to its place.

Second, the answer

11.The two terminals of A and B are 560 kilometers away. A boat sails from terminal A for 20 hours to reach terminal B. It is known that the boat travels 24 kilometers per hour in still water. How long does it take for the boat to return to terminal A?

12. In still water, the speed of ship A is 22 kilometers per hour, and the speed of ship B is 18 kilometers per hour. Ship B first sails from a certain port and sails down the water. After 2 hours, ship A leaves in the same direction. 4 kilometers per hour, how many hours can A ship catch up with B ship?

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