Harmonic mean - practice for 14 year olds - last page
Number of problems found: 98
- Blueberries
Marie earns 3 liters of blueberries for 3.4 hours, and Peter 2.4 liters for 2.9 hours. How long do they pick one liter together? - Two valves
Water fills the pool with two valves for 11 days. After 7 days, the workers stopped the first and second valve fill pool for 7 days. How many days took to fill the pool of each of the valves individually? - Average
What is the average speed of the car, where half of the distance covered passed at a speed of 64 km/h and the other half at 82 km/h? - Parquet floor
Three workers laid the parquet floor for 2.301 hour. The first would do this work alone 7 hours, the second in 6 hours. For how many hours would fulfill this work for the third worker if he worked alone?
- Inflow - outflow
The tank will fill by inflow for 56 minutes and empties by outflow for 77 minutes. How long does it take to fill the tank if it is also opened to the inflow and outflow? - Painters
The first painter painted the fence himself for 4 hours, the second painter 1.2 hours sooner than the first, and the third painter slowest up to 16 hours. How long took them to paint the fence if they worked together? - Workers
Two workers, A and B, will be done work together for 15 days. They worked together for 13.5 days. Then A worker became ill, and worker B finished the job alone for 7.5 days. If every worker was working alone, how many days took the whole work for workers - Madams
During the spring cleaning, ladies were going to wash the windows. Mother takes to wash all the windows 5 hours, the grandmother takes 3 times longer, and Paula washes all windows in 2 hours. How many hours will you spend washing the windows of this "wome - 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? - 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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