A geometry problem by A Former Brilliant Member

Geometry Level 1

How many triangles are in this picture?


The answer is 13.

A Former Brilliant Member by A Former Brilliant Member

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2 solutions

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Zyberg Nee
Oct 28, 2017

Start counting the triangles from the biggest one.

| Sum = S = 1

Count in the triangles that are made up of four other.

| S = 1 + 3 = 4

Finally, count in the smallest triangles.

| S = 4 + 9 = 13

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