Three friends went to a restaurant.They have had dinner of Rs.75/-. So each of them had paid Rs.25 to the waiter to give it to the cash counter.The Owner of the restaurant gave them a concession of Rs. 5. From that the waiter took Rs.2 and gave them Rs.3 back. From that each of them take Rs. 1.That means they gave 24 rs each.So the total is (24+24+24)=72 and the waiter take Rs. 2. Sothe total is 72+2=74. But at first they gave Rs. 75. So what happened to one rupee?