How many triangles are there?

Solution

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Since the triangles 🔺 are all “equilateral”, we count the number of occurrences for each equilateral triangle size as follows:

(i) Number of equilateral triangles with side length 3 units = 1

(ii) Number of equilateral triangles with side length 2 units = 3

(iii) Number of equilateral triangles with side length 1 unit = 9

So,

Total = 1 + 3 + 9 = 13 triangles (Answer)