Pipe A can fill an empty cistern in 4.5 hours. Whereas along with Pipe B, it can fill it in 2.25 hours. If only Pipe A is turned on for half an hour after which Pipe B is also turned on, how long will it take in all to fill the cistern?
1
2 hours 30 minutes
2
2 hours
3
2 hours 20 minutes
4
2 hours 15 minutes