Only 4 Weights Puzzle - Solution

The Puzzle:

You have a balance scale with four weights. With these four weights you must balance any whole number load from 1kg all the way up to 40kg.

How much should each of the four weights weigh?

(You may place weights on both sides of the scale at the same time.)

Our Solution:

You need a 1kg, 3kg, 9kg, and a 27kg weight.

You can achieve different weights by changing the sides of the weights.

For instance, a 3kg weight on the right and a 1kg weight on the left would let you weigh 2kg on the left.

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