On a balance scale, two identical square blocks balance perfectly with one circle block and one triangle block. Also, one circle block balances perfectly with one square block and one triangle block. How many triangle blocks are needed to balance exactly one square block?
Two triangle blocks.
Substituting the weight of the circle (1 square + 1 triangle) into the first balance gives: 2 squares = (1 square + 1 triangle) + 1 triangle. Simplifying gives 2 squares = 1 square + 2 triangles. Subtracting 1 square from both sides leaves 1 square = 2 triangles.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
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