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प्रश्न
Two taps can fill a cistern in 10 hours and 8 hours respectively. A third tap can empty it in 15 hours. How long will it take to fill the empty cistern, if all of them are opened together?
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उत्तर
First tap can fill a cistern in 10 hours
Second tap can fill the cistern in 8 hours
Third tap can empty the cistern in 15 hours
∴ First tap's 1 hour's work = `1/10`
Second tap's 1 hour's work = `1/8`
and third tap's 1 hour's work = `1/15`
If all of them are opened together, then
heir one hour's work = `1/10 + 1/8 - 1/15`
`= (12 + 15 - 8)/120 = (27 - 8)/120 = 19/120`
∴ They can fill the cistren in =`120/19` hours
`= 6 6/19` hours
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संबंधित प्रश्न
A can do a piece of work in 4 days and B can do the same work in 5 days. Find, how much work can be done by them working together in:
- one day
- 2 days
What part of work will be left, after they have worked together for 2 days?
Joseph and Peter can complete a work in 20 hours and 25 hours respectively. Find :
(i) work done by both together in 4 hrs.
(ii) work left after both worked together for 4 hrs.
(iii) time taken by Peter to complete the remaining work.
A racing car covered 600 km in 3 hours 20 minutes. Find its speed in metre per second. How much distance will the car cover in 50 sec?
The speed of sound in air is about 330 ms-1. Express this speed in kmh-1. How long will the sound take to travel 99 km?
These log boats do not go very far. If the wind is helpful, then travel about 4 km in one hour.
Guess how far you can go in one hour if you walk fast.
Look at the different types of boats.
Some boats have motors and go further into the sea. since they go far out they can catch more fish. These boats travel faster, at a speed of about 20 km in one hour.
How much time will they take to go 85 km?
In one trip the logboat brings about 20 kg of fish. But other types of boats bring a bigger catch as given in the table. The table also shows the speed of each type of boat, which is how far each boat goes in one hour. Look at the table and calculate -
- About how much fish in all will each type of boat bring in seven trips?
| Type of boat | Catch of fish in one trip (in kg) |
Speed of the boat (how far it goes in one hour) |
| Log boat | 20 | 4 km per hour |
| Long tail boat | 600 | 12 km per hour |
| Motorboat | 800 | 20 km per hour |
| Machine boat | 6000 | 22 km per hour |
In one trip the logboat brings about 20 kg of fish. But other types of boats bring a bigger catch as given in the table. The table also shows the speed of each type of boat, which is how far each boat goes in one hour. Look at the table and calculate -
- If a long tail boat has to travel 60 km how long will it take?
| Type of boat | Catch of fish in one trip (in kg) |
Speed of the boat (how far it goes in one hour) |
| Log boat | 20 | 4 km per hour |
| Long tail boat | 600 | 12 km per hour |
| Motorboat | 800 | 20 km per hour |
| Machine boat | 6000 | 22 km per hour |
The SI unit of speed is:
A runner covers 900 m in 3 min. Speed in m s⁻¹ is:
