a. Keep three coins each on the weighing machine, one outside. If both sides are equal, the coin kept out is the fake. If left side of the weighing machine moves down the fake coin is one among the three on the right side.
b. Remove all coins from the left side of the machine. From the three coins on the right side, keep one out and keep one each on the left and right sides of the weighing machine. If bothe sides remain equal, the cin kept out is the fake. Else if the left side moves down, the coin on the right side is fake and vice versa.
Ok here is the one for 1........
a. Keep three coins each on the weighing machine, one outside. If both sides are equal, the coin kept out is the fake. If left side of the weighing machine moves down the fake coin is one among the three on the right side.
b. Remove all coins from the left side of the machine. From the three coins on the right side, keep one out and keep one each on the left and right sides of the weighing machine. If bothe sides remain equal, the cin kept out is the fake. Else if the left side moves down, the coin on the right side is fake and vice versa.