Harmonic mean - practice for 13 year olds - page 3 of 6
Number of problems found: 104
- Tributaries 7678
We filled the pool with two tributaries: the first in 5 hours and the second in 8 hours. The father came and drained 1/8 of the water. How long before the pool fills with both tributaries? - 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? - Three pumps
We are filling the pool. The pool would fill the first pump in 12 hours and the second in 15 hours. If all three pumps ran simultaneously, they would fill the pool for 4 hours. How long would the pool fill only with the third pump? - Half-filled 7336
The water tank is filled with the first inflow in one hour and 10 minutes and the second in 60 minutes. How many minutes will the tank be half-filled with both inlets if the second outlet is opened 12 minutes later?
- Calculation 7334
In a computer center, one computer would work 12 hours to solve a task, and another, more powerful, would solve the same task for 10.5 hours. If both computers work together, the calculation time would be reduced for a certain period. Calculate how long i - The factory
The factory z can complete an order in 12 days, factory p in 18 days. How many days does an order completed when the first two days work only the factory z and then both factories? - Water reservoir
One drain hole emptied the water from the tank for 20 hours, with the second drain for 30 hours. How long will the water drain from this tank if we open two drains simultaneously? - 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 - A report
Maricris can type a committee report in 5 hours. Jane helped Maricris, and together they finished the report in 3 hours. How long would it take Jane to complete the report she had worked on alone?
- 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? - Soldier
An experienced soldier digs a good trench in 30 hours. Two soldiers dug the same trench every 40 hours. How many hours will the ditch dig all three together? - Summer tires
Three tire servants must change the summer tires on six cars in 2 hours. Mark's replacement would take 4.5 hours, Jirka would do it in 3 hours and 10 minutes, and Honza in 4 hours. Will they be able to replace all tires at the desired time? - Evening shift
While working the evening shift, Officer K took 8 hours to complete a task at his workstation, and Officer M took 10 hours to complete the same task at his workstation. How many hours would it take Officer K and M to complete the same task, each working a - Together 3
If Sally can paint a house in 4 hours, and John can paint the same house in 6 hours, how long will it take for both of them to paint the house 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? - Minute average
In a factory, four workers are assigned to complete an order received for dispatching 1400 boxes of a particular commodity. Worker A takes 4 minutes per box, Worker B takes 6 minutes per box, C takes 10 minutes per box, and D takes 15 minutes per box. Fin - Three painters
The three painters have painted bridges. The first would work done in 5 days, the second in 6 days, and the third in 7.5 days. How long will the bridge work if they work together? - Flying
The airplane from Prague to Bratislava was flying at a speed of 60 km/h less and back by 70 km/h greater than the original speed. What was the original speed if the plane returned to Prague according to the timetable? - 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?
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