The Kid Should See This

Can you solve the unstoppable blob riddle?

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A shooting star crashes onto Earth and a hideous blob emerges. It creeps and leaps, it glides and slides. It’s also unstoppable: no matter what you throw at it, it just re-grows and continues its rampage. The only way to save the planet is to cut the entire blob into precise acute triangles while it sleeps, rendering it inert. Can you stop the blob from destroying the planet?

This TED-Ed math problem is great for the classroom or at home. Get a paper and pencil, and pause this unstoppable blob riddle video at the 2-minute mark to figure out how you can cut the triangle into acute triangles—triangles with angles that are less than 90°—with fewer than 7 cuts with the nano-laser satellite ray.

acute triangle riddle
stop the blob riddle rules
Need a hint? Think about pizza. Then watch these videos next: Matchstick Triangle Puzzle, The Remarkable Way We Eat Pizza, and The Mathematical Secrets of Pascal’s triangle.

Bonus: Types of Triangles, a Flocabulary math music video.

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