Odd Brick Out
Riddle: Jack has 8 bricks, 7 of them weigh the same but one is slightly heavier. Using a balance scale, how can Jack find the heavier brick in two weighings?
Answer: First, he splits them into piles of 3, 3, and 2 bricks.
Then, he weighs both groups of 3 with each other. If they balance he knows the brick is one of the 2 unweighed bricks and he can weigh them to find the heavier one.
If the stacks of 3 bricks do not balance, he will weigh 2 of the 3 bricks.
If they balance he will know the brick left unweighed is heavier, or if they do not balance, he will find the heavier one.
Source: https://www.riddles.com/index.php/1533
