Harmonic mean + expression of a variable from the formula - practice problems - last page
Number of problems found: 33
- Three painters
The three painters have painted bridges. The first would work done in 5 days, the second in 6 days, and the third in 7.5 days. How long will the bridge work if they work together? - Three pumps
The water tank is emptied with the first pump in 6 hours, with the second pump in 2 hours. In order to be emptied in 1 hour, all three pumps had to be started at once. How long will it take to empty the tank by only the third pump? - Flying
The airplane from Prague to Bratislava was flying at a speed of 60 km/h less and back by 70 km/h greater than the original speed. What was the original speed if the plane returned to Prague according to the timetable? - In and out
The empty tank is filled in 12 minutes and empty in 16 minutes. How long does it take to fill if we forget to close the drain? The tank has 1000 liters of volume.
- ICE train
German runways test a new ICE train between Munich and Berlin. The train runs to Berlin at a slow speed of 100 km/h. Back from Berlin goes faster. How quickly did the train have to go on a return trip so that the average train speed for both journeys woul - Oil tank and pipes
Two oil pipelines can fill the underground oil tank. The first is filled in 72 hours, and the second in 48 hours. How many hours from when the first pipeline began to fill the oil is necessary to start filling it with the second to fill in 1 and 1/2 days? - Pumps 4912
A pool with one pump fills in 14 hours and the other in 15 hours. How long will the pool fill when both pumps are used? - Kilometers 4604
The tourist traveled 78 km in three hours. For part of the journey, he traveled by bus at an average speed of 30 km/h, and for the rest, he walked at an average speed of 6 km/h. How long did he walk, and how many kilometers did he walk? - Independently 3874
Josef would do the work himself in 5 hours. Josef and Michal would do the work together in 3.5 hours. Determine how long it would take Michal to do the job independently.
- Determine 3851
Michal would cut the fence himself in 12 hours. It would take Michal and Juraj 8 hours together. Determine how long it would take for Juraj to do the job. - Cleaners
Milan would clean up the room for 2.5 hours, and Eric would take 10 hours. How long do they sweep the room together? - Garden
Father dug up the garden in 11 few hours. Son in 15 hours. How many hours does it take to dig up the garden together? - Fire tank
The whole fire tank was discharged once in 5 days by first out by a second in $n day. Once firefighters pumped out 6/13 of water out from the tank and then let the water flow out both drains. How long does it take empty the tank?
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