#### If a pipe can fill a cistern in 12 hours and another pipe can fill the same cistern in 15 hours, how long will it take for both the pipes to fill the cistern working together? 1. [ ] 5 hours and 30 minutes 2. [ ] 6 hours 3. [x] 6 hours and 40 minutes 4. [ ] 5 hours and 20 minutes #### If a pipe can empty a completely filled cistern in 10 hours, and another pipe can empty the same cistern in 15 hours, how long will it take for both the pipes to empty the cistern working together, if the cistern was initially completely filled? 1. [ ] 5 hours and 30 minutes 2. [x] 6 hours 3. [ ] 4 hours and 40 minutes 4. [ ] 5 hours and 20 minutes #### If three pipes can fill a cistern in 20 hours, how long will it take for two pipes to fill the cistern if the third pipe is leaking and it fills the cistern 1 hour slower? 1. [ ] 12 hours 2. [ ] 13 hours 3. [x] 15 hours 4. [ ] 18 hours #### If a pipe can fill a tank in 15 hours, and another pipe can fill the same tank in 20 hours, how much time will the second pipe save if it works in conjunction with the first pipe for 6 hours? 1. [ ] 2 hours 2. [ ] 2 hours and 30 minutes 3. [x] 3 hours 4. [ ] 3 hours and 30 minutes #### If a pipe can fill a cistern in 24 minutes, and another pipe can empty the same cistern in 30 minutes, how long will it take for the first pipe to fill the cistern if both pipes work simultaneously at the same time? 1. [ ] 11 minutes 20 seconds 2. [x] 12 minutes 3. [ ] 13 minutes 20 seconds 4. [ ] 14 minutes