Harmonic mean - practice problems - last page
Number of problems found: 171
- Car
The car goes from point A to point B at speed 86 km/h and back 53 km/h. If it goes there and back at speed 67 km/h trip would take 10 minutes shorter. What is the distance between points A and B? - Tanker
The first pump can empty an oil tanker in 4.9 hour. The second pump can empty a tanker in 8 hours. If the first pump started at 4:00 and the second 1.4 hour later, at what time will the tanker be empty? - Steamship
Between the two ports on the river is going steamship. The journey there and back takes 8:42. Downstream steamship traveling at 20 km/h, upstream 9 km/h. What is the distance between the ports? - Workers
Two workers would fulfill a certain task when working together for 5 days, the first if he worked himself done work in 13 days. How many days will the second worker do the whole job?
- Reciprocal
What is the reciprocal of the sum of the reciprocals of 7 and 6? - 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? - Pool
If water flows into the pool by two inlets, fill the whole for 20 hours. The first inlet filled the pool 8 hour longer than the second. How long does the pool take to fill with two inlets separately? - 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
- Electronics: Resistors in parallel
Concerning calculating the resistance of the parallel combination of resistors: (1)/(R) = (1)/(R1) + (1)/(R2) Calculate the R, if R1 = 17Ω a R2 = 20Ω - 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?
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