The are 3 friends living together in one home the pay together for the bill of home they combin the money and payed each person give 10 in addition 30 birr they pay for home bill. Than one day the owner of the house send his son to take the monthly payment and the boy take the money to his dad and his dad give the 5 birr tip and the boy give them 5 birr than the 3 friends take 3 birr and dived each other each one of them take 1 birr and the half 2 birr they give to the boy. Each of them collect 10+10+10=30birr payment now they get 1 birr for each of them that means 9+9+9=27birr the boy take 2 birr 27+2=29 Who take the one birr the were 30 birr or were the 1 birr disappeared?