| Question | Two pipes can fill a tank in 6 hours and 8 hours respectively. A third pipe can empty the same tank in 12 hours. If all the pipes start working together, how long it will take to fill the tank? | |
| Type | multiple_choice | |
| Option | 4 hours | incorrect |
| Option | 4.5 hours | incorrect |
| Option | 4.8 hours | correct |
| Option | 5.2 hours | incorrect |
Part of the tank filled by two pipes in one hour = 1/6 + 1/8
Part of the tank emptied by the third pipe in one hour = 1/12
∴ Net part of the tank filled in one hour = 1/6 +1/8 – 1/12
5/24 Part of tank can be filled in one hour
∴ The whole tank will be filled in 24/5 = 4.8 hours
