Harmonic mean - practice for 14 year olds
Number of problems found: 95
- Reciprocal
What is the reciprocal of the sum of the reciprocals of 7 and 6? - Sequence 11
What is the nth term of this sequence 1, 1/2, 1/3, 1/4, 1/5 ...? - Working together
One painter painted the nursery in 10 days, the second in 8 days. How many days will the nursery be painted if they work together? - Average speed
The car drove from city A to city B at 40 km/h and back to city A at a speed of 80 km/h. What was the average speed of the car? - Tributaries
The first tributary fills the pool with water in 15 hours. The second tributary fills the pool in 10 hours. For how many hours is the pool filled with both tributaries? - Apartment 81654
A woman cleans an apartment in 8 hours and a man in 10 hours. How many hours will they clean together? - 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? - Excavators 82208
Two excavators dig a pit in 12 days. How much shorter will this job take if 8 excavators dig the hole? In 3 or 9 days? - Together 5931
The tank will be filled with the first inlet in 5 hours and the second in 12 hours. How long would it take to fill the tank together? - Bricklayers
When a bricklayer works to redeem the house in 8 days, the other bricklayer will be finished in 10 days. How long will it take to make three such houses together? - Turners
Two turners perform joint work in 3 hours. The first-turner would perform the job himself in 7 hours. How long would the same job last for a second-turner if he worked alone? - 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? - Painter Pavel
Painter Pavel painted the fence for 16 hours, and painter Petr the same fence painted for 13 h. How long should it take to paint the fence together? - Completes 4234
The worker completes the work in 12 days, the second in 10 days. The first worker kicks himself for four days, then the second worker comes. How long will it take to dig? - Pond
Workers will empty a pond with two open floodgates in 20 days. A larger floodgate will empty the whole pond in 30 days. For how long would he be emptied with a smaller floodgate? - Two diggers
There are two diggers. One digger digs a pit 77 hours second, digging 1.2 times faster. a) how long took to dig a pit second digger b) how long took it to dig together - 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? - 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? - 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 - Apartment 71114
A father and son paint the apartment together in 6 hours. My father would paint the apartment in 9 hours. In how many hours would the son paint the apartment himself?
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