** Puzzle: **You are provided with 8 identical balls and a measuring instrument. 7 of the eight balls are equal in weight and one of the eight given balls is defective and weighs less. The task is to find the defective ball in exactly two measurements.

__Solution__:

**Step 1:**Divide the balls into three categories(C1, C2 and C3).- Let C1 consist of balls B1, B2 and B3.
- Let C2 consist of balls B4, B5 and B6.
- Let C3 consist of balls B7 and B8.

**Step 2:**Put C1 on one side of the weighing machine and C2 on the other.

This can give rise to 3 conditions:- Condition 1:
*C1 equals C2* - Condition 2:
*C1 < C2* - Condition 3:
*C1 > C2*

- Condition 1:

Now let’s analyse the three conditions to find the defective ball:

If C1 is equal C2, then C3 has the defective ball. Now measure the weights of ball B7 and B8.__Condition 1__:- If B7 < B8, B7 is defective
- If B7 > B8, B8 is defective.

If C1 < C2, then C1 has the defective ball. Now measure the weights of ball B1 and B2.__Condition 2__:- If B1 equals B2, B3 is defective.
- If B1 < B2, B1 is defective.
- If B1 > B2, B2 is defective.

If C1 > C2, then C2 has the defective ball. Now measure the weights of ball B4 and B5.__Condition 3__:- If B4 equals B5, B6 is defective.
- If B4 < B5, B4 is defective.
- If B4 > B5, B5 is defective.

- Puzzle | Black and White Balls
- Puzzle | 10 Balls in 5 Lines
- Puzzle 15 | (Camel and Banana Puzzle)
- Puzzle 24 | (10 Coins Puzzle)
- Puzzle 27 | (Hourglasses Puzzle)
- Puzzle 28 | (Newspaper Puzzle)
- Puzzle 29 | (Car Wheel Puzzle)
- Puzzle 31 | (Minimum cut Puzzle)
- Puzzle 33 | ( Rs 500 Note Puzzle )
- Puzzle 34 | (Prisoner and Policeman Puzzle)
- Puzzle 36 | (Matchstick Puzzle)
- Puzzle 38 | (Tic Tac Toe Puzzle)
- Puzzle 39 | (100 coins puzzle)
- Puzzle 51| Cheryl’s Birthday Puzzle and Solution
- Puzzle 81 | 100 people in a circle with gun puzzle
- Puzzle 85 | Chain Link Puzzle
- Puzzle | Elevator Puzzle
- Puzzle | 3 Priests and 3 devils Puzzle
- Puzzle 6 | (Monty Hall problem)
- Puzzle | (4 Matchstick Problem)

## Recommended Posts:

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.