Can you help me with a clear and concise answer to this brain teaser?

3 people book into a hotel room. It costs �30 so they pay ten pounds each. After paying, the receptionist realises they've paid to much as the room should have cost only �25. Rather than cause an argument over them splitting �5 she keeps �2 and gives them a pound each so they each paid �9. 3 x 9 = 27 + 2 = 29 where did the other �1 go?