Find The Heaviest Ball

Given 27 table tennis balls, one is heavier than the others.

What is the minimum number of weighings (using a two-pan balance scale) needed to guarantee identifying the heavy one? The other 26 balls weigh the same.

Here is how to identify the heavier ball.

Identifying The Heavier Ball

 What was the task given?

We need to use the scale only 3 times.

1. Divide the 27 balls into 3 groups of 9 balls each. 

2. Use the scale to weigh 2 groups. This will tell us which group has the heavier ball. 

    If the scale is balanced then third group must be having heavier ball

3. Now, divide the 9 balls into 3 groups of 3 balls each and weigh 2 groups, and identify the group which has the heavier ball. Again, if the scale is balanced then the third group must be having the heavier ball.

4. From the heavier group, weigh 2 balls to determine the heavier ball. And, if the scale is balanced then the third ball must be heavier.