Reason + harmonic mean - practice problems
Number of problems found: 23
- Triangle 8320
Is there a triangle with heights of 4, 7, and 10 meters? - Mow the lawn
Dano would mow the lawn in 12 hours and Milada in 16 hours. How long will it take the lawn mow together? - Timber log
The ship goes from point x to y. Downstream it takes 4 hours, and upstream 6 hours. How long does it take from a point x to y a log? - Average 4458
The first third of the track was driven by a car at a speed of 15 km/h, the second third at a speed of 30 km/h, and the last third at a speed of 90 km/h. Find the average speed of the car. - Drinking water
A man drinks a keg of water in 36 days, and a woman drinks in 65 days. How many days do they consume a keg together? - Tractors
Fields go plow two tractors with various performances. The first tractor plows the whole field in 11 hours. The second tractor plows the whole field 19 hours longer. How long does it take to plow the whole field with two tractors? - Cyclist
The cyclist goes uphill 10 km for 50 minutes and downhill minutes for 29 minutes. Both applied to the pedals with the same force. How long does he pass 10 km by plane? - Energy saving
They released three different independent inventions saving 15%, 17%, and 16% energy. Some considered that while the use of these inventions, the total savings will be 15% + 17% + 16% = 48%. Is this true? How much will the percent of energy save all three - Uphill and downhill
The cyclist moves uphill at a constant speed of v1 = 10 km/h. When he reaches the top of the hill, he turns and passes the same track downhill at a speed of v2 = 40 km/h. What is the average speed of a cyclist? - Simultaneously 2570
Two cyclists will set off simultaneously from one place on the circular cycling track. How long before they meet? Do you know that Karel will drive in 6 minutes and Laco in 10 minutes? - Minutes 7177
The tank holds 140 liters of water. The tank is filled with a tap in 5 minutes, and the drain is emptied in 7 minutes. How long will it take for the empty tank to fill if we open the faucet and drain? - Harvesters
The first harvester will harvest the grain from the field in 20 hours, and the second, the more powerful in 10 hours. How long will it take to harvest this field by both harvesters if the second harvester has to be set up first, which takes 2 hours? The f - 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? - Kilometers 7631
At 8:00, Peter set out on a hike at 5 km/h. At 9:12, Michal followed him on a bike at a speed of 20 km/h. At what time did Michal Petra run, and how many kilometers did he cover? - Forth and back
Car drive from point A to point B at a speed of 78 km/h and back at 82 km/h. If I went there and back at a speed of 81 km/h journey would take five minutes less. What is the distance between points A and B? - Three drivers
Three drivers driving in the same direction found that they have the same amount of gasoline. The first is enough to go 6 km, 4 km, second and third 3km. Gasoline they divided, so all three just drove to the nearest petrol station. How many km away was a - Two cities
The car goes from city A to city B at an average speed of 70 km/h and back at an average speed of 50 km/h. If it goes to B and back at an average speed of 60 km/h, the whole ride will take 8 minutes less. What is the distance between cities A and B? - Water current
John swims upstream. After a while, he passes the bottle, and from that moment, he floats for 20 minutes in the same direction. He then turns around and swims back, and from the first meeting with the bottle, he sails 2 kilometers before he reaches the bo - Four pavers
Four pavers would pave the square in 18 days. How many pavers do you need to add to the done work in 12 days? - Aircraft angines
The aircraft's two engines are enough to supply the fuel for five hours of operation. However, one of the engines has malfunctioned and thus consumes one-third more fuel. How long can the plane be in the air before it runs out of fuel? After an hour of ma
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