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Shape weighing brainteaser

By David Shaw, 28 October 2020

By Rok Willesee

Difficulty: Tricky

A scientist was looking back at notes they made about their experiments. Unfortunately, in one experiment the scales didn’t work. Can you help them work out what the weight should be in the final experiment?

Credit: CSIRO/Diya Dhaliwal

You can assume that two objects that are the same shape weigh the same amount.

Scroll down or click for a hint, or the answer!

Brainteaser hint

First, see if you can work out what one square weighs.

Brainteaser answer

The third scale has two squares and weighs 8. That means one square must weigh half of 8, which is 4.

The second scale has a triangle and square and weighs 5. If the square weighs 4, the triangle must weigh 1.

The first scale has a triangle and circle and weighs 3. If the triangle weighs 1, then the circle must weigh 2.

The final scale has a square, circle and triangle. The square weighs 4, the circle weighs 2 and the triangle weighs 1 for a total of 7.

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