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Three taps A, B and C can fill a tank in 12, 15 and 20 hours respectively. If A is open all the time and B and C are open for one hour each alternatively, the tank will be full in :
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- 6 hours
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6 1 hours 2 - 7 hours
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7 1 hours 2
Correct Option: C
On the basis of given details in question ,
| Part filled by A and B in 1 hour = | + | = | = | .......(i) | ||||
| 12 | 15 | 60 | 20 |
| Part filled by A and C in the next 1 hour = | + | = | = | ||||
| 12 | 20 | 60 | 15 |
| Part filled in 2 hours = | + | = | = | ||||
| 20 | 15 | 60 | 60 |
| ⇒ Part filled in 6 hours = | |
| 60 |
| Remaining part = 1 - | = | = | |||
| 60 | 60 | 20 |
This part will be filled by (A+B) in 1 hour. [By (i)]
∴ Total time taken = 7 hours
