Harmonic mean - examples
Looking for help with calculating harmonic mean
- 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 total average train speed for both journeys
- Mow the lawn
Dano would mow the lawn in 12 hours and Milada in 16 hours. How long will take the lawn mow together?
If water flows into the pool by two inlets, fill the whole for 9 hours. First inlet filled pool 8 hour longer than second. How long pool is filled with two inlets separately?
A man drinks a barrel of water for 31 days, woman for 58 days, for how many days they drink barrel together?
Fields go plow two tractors with various performance. The first tractor plow whole field in 5 hours, the second tractor plow whole field 5 hours longer. How long take plow whole field with two tractors?
Cyclist goes uphill 1 km for 6.3 minutes and downhill minutes for 2.1 minutes, both applied to the pedals same force. How long he pass 1 km by plane?
Car goes from point A to point B at speed 70 km/h and back 76 km/h. If they goes there and back at speed 73 km/h trip would take 19 minutes shorter. What is distance between points A and B?
Workers A and B will done work together for 20 days. They worked together 18 days. Then A worker became ill and worker B finish the job alone for 11 days. If every worker was working alone, how many days took whole work for worker A and B?
Two workers fulfill a certain task when working together for 7 days, the first if he worked himself done work in 18 days. How many days will do whole job a second worker?
- Pedestrian up-down hill
Pedestrian goes for a walk first at plane at 4 km/h, then uphill 3 km/h. Then it is in the middle of the route, turns back and goes downhill at speed 6 km/h. Total walk was 6 hours. How many kilometers went pedestrian?
During the spring cleaning ladies going to wash windows. Mother takes wash all the windows 5 hours, the grandmother 3 times longer and Paula wash all windows in 5 hours. How many hours will spend washing the windows this "women's team" if working togethe
Father dig up the garden in 13 hours. Son in 18 hours. How many hours take dig up the garden together?
- Painter Pavel
Painter Pavel painted the fence for 20 hours and painter Petr the same fence painted for 17 h. How long should take painted the fence together?
An oil tanker can be emptied by the first pump in 4.4 hours. Second pump can empty an tanker in 7.8 hours. If the first pump started at 8:00 and second 1.4 hour later, at what time will the tanker be empty?
Between the two ports on the river is going steamship. The journey there and back takes 14:49. Downstream steamship traveling at 21 km/h, upstream 9 km/h. What is the distance between the ports?
Marie earns 1.8 liters of blueberries for 1.2 hours, Peter 2.6 liters for 1.2 hours. How long have earns together one liter?
- Three workers
Three workers A, B, C have to work on a specific task. Workers A and B completed whole task in 25 days, B together with C for 16 days, A together with C for 10 days. How long it would take to complete the task every one of them alone? How long it would.
- Electronics: Resistors in parallel
From relation for calculating the resistance of parallel combination of resistors: ? Calculate the R, if R1 = 8kΩ a R2 = 18kΩ
In the workshop are three machines. The first is treated 350 parts for 4.3 hours, the second is treated 490 parts for 4.6 hours and the third is treated 360 parts for 3.7 hours. How long will take to make 3080 parts if worked all three machines at the.
- Two valves
Water fill the pool by two valves for 16 days. After 6 days the first valve was stopped and the second valve fill pool for 12 days. How many days took to fill the pool each of the valves individually?
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