By Rok Willesee
Difficulty: Fun
An engineer has asked you to help him count the number of triangles in this roof truss. He thinks there are five, but his boss thinks there are more. How many triangles can you see? Credit: CSIRO/Diya Dhaliwal Scroll down or click for a hint, or the answer! Small triangles together can make bigger triangles. When counting shapes, it’s important to keep organised. Let’s count the triangles in groups, based on size: • There are four small triangles, near the top. All together, there are 4 + 2 + 1 = 7 triangles. For more brainteasers and puzzles for kids, subscribe to Double Helix magazine!
Brainteaser hint
Brainteaser answer
• There are two medium sized triangles. One is at the bottom right, and the other surrounds the four small triangles.
• The whole truss makes up one big triangle.
![Triangle divided into multiple triangles.](<p>Credit: CSIRO/Diya Dhaliwal</p>
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