An empty swimming pool can be filled to capacity through an inlet pipe in 3 hours and it can be completely drained by a drainpipe in 6 hours. If both pipes are fully open at the same time, in how many hours will the empty pool be filled to capacity?

প্রশ্নঃ An empty swimming pool can be filled to capacity through an inlet pipe in 3 hours and it can be completely drained by a drainpipe in 6 hours. If both pipes are fully open at the same time, in how many hours will the empty pool be filled to capacity?