Finding the heaviest coin (Solution)

Answer to the problem

1. Start by dividing the balls in groups of three with approximately the same amount, in this case, in two groups of three and one group of two. To begin we start putting one of each group that has three balls on each side of the scale. If the scale is balanced the heaviest ball must be on the group that was not weighted and if the scale was unbalanced, the heaviest ball is on the heaviest plate of the scale.

2. After identifying where the heaviest ball is, put all the other balls in the area of disposal. Split the balls in the heaviest group and put one ball in each plate of the scale. Yet again if the scale is balanced, the heaviest ball is the one that was not weighted and if the scale is unbalanced, the heaviest ball is the one that we were looking for.

3. Just to check if you chose the correct ball, put it on the test area and see if it is in fact the heaviest one. If so, you completed the challenge with success.

Observation: One alternative to the usage of the “test area” is to compare the suspected heaviest ball with any other ball. If the scale is balanced, you chose the wrong ball and needs to try again. If the scale is unbalanced, the heaviest ball is the one that is on the lowest plate (it is heavier).