Harmonic mean - practice problems - page 7 of 10
The harmonic mean is a type of average that is particularly useful for calculating rates, ratios, or situations involving reciprocals.It is calculated as the reciprocal of the arithmetic mean of the reciprocals of a set of numbers.
The harmonic mean is often used when dealing with averages of quantities like speed, where time and distance are inversely related. It tends to be less affected by extremely large values in a dataset, making it more appropriate for skewed distributions compared to the arithmetic mean.
A key property of the harmonic mean is that it is always less than or equal to the arithmetic mean and the geometric mean for any set of positive numbers.
It is commonly applied in finance, such as calculating the average price-to-earnings ratio, and in physics, such as finding equivalent resistance in parallel circuits. The harmonic mean is not suitable for datasets containing zero or negative values, as it is undefined in such cases.
Number of problems found: 186
- 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? - Two brothers
Two brothers want to collect 20 kg of chestnuts. If only Marek collected, he would make it in 30 minutes. It would take Milan 10 minutes longer. How long after Mark does Milan have to start collecting to be finished in 18 minutes? - 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? - 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?
- In and out
The empty tank is filled in 12 minutes and empty in 16 minutes. If we forget to close the drain, how long does it take to fill? The tank has 1000 liters of volume. - The pool
The pool has a volume of 40 m3, and the water temperature is 20 °C. How much water at 100 °C should we pour into the pool to increase the water temperature by 5 °C? - ICE train
German runways test a new ICE train between Munich and Berlin. The train runs to Berlin at a slow speed of 110 km/h. Back from Berlin goes faster. How quickly did the train have to go on a return trip so that the average train speed for both journeys woul - Mow the lawn
Dano would mow the lawn in 12 hours and Milada in 16 hours. How long will it take the lawn mow together? - 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?
- Pumping
The tank is filled with a larger pump in 12 hours and with a second pump in 15 hours. For how long does the tank fill when both pumps are switched on at the same time? - Sequence 11
What is the nth term of this sequence 1, 1/2, 1/3, 1/4, 1/5 ...? - Oil tank and pipes
Two oil pipelines can fill the underground oil tank. The first is filled in 72 hours, and the second in 48 hours. How many hours from when the first pipeline began to fill the oil is necessary to start filling it with the second to fill in 1 and 1/2 days? - Pumps 4912
A pool with one pump fills in 14 hours and the other in 15 hours. How long will the pool fill when both pumps are used? - Probability 4665
We have three series of products. We select one product for quality control. Determine the probability of finding a low-quality product if the first batch contains 2/3, the second batch 7/9, and the third batch 3/4 quality products.
- Two rooms
If a woman cleans the room in 30 minutes and a man in 90 minutes, how long will it take them to clean two rooms? - Kilometers 4604
The tourist traveled 78 km in three hours. For part of the journey, he traveled by bus at an average speed of 30 km/h, and for the rest, he walked at an average speed of 6 km/h. How long did he walk, and how many kilometers did he walk? - Together 4511
One tractor would sow the field in 3 hours and the other in 7 hours. How long before the fields grow together? - Average speed
The first third of the track was driven by a car at a speed of 15 km/h, the second third at a speed of 30 km/h, and the last third at a speed of 90 km/h. Find the average speed of the car. - 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?
Michal and Dorota would do the work together in 2.25 hours. If Dorota had to do it herself, it would have taken her 6 hours longer than Michal. Determine when Dorota will do the work herself and when Michal will do it himself.Do you have homework that you need help solving? Ask a question, and we will try to solve it. Solving math problems.
