3 friends rented a room in a hotel and it cost them RM30. So each of the 3 friends paid RM10 to make it RM30 without knowing that it only cost them RM25 as the room is under promotional rate. So the receptionist, don't know how to give the money fairly, gave RM3 back whereas each of th 3 receive RM1 and another RM2 is for her tips.
S0, 9 x 3 = 27
27 + 2 = 29
But they gave Rm30 in the first place.
So where's the RM1?