Example of geometric patterns using matchsticks to form triangles.

Final Answer:
The number of matches increases by 3 for each additional triangle. So the pattern is: start with 3 matches for 1 triangle, and add 3 more matches for each new triangle.

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Explanation:
Let’s look at the table:

- For 1 triangle: 3 matches
- For 2 triangles: 6 matches
- For 3 triangles: 9 matches
- For 4 triangles: 12 matches
- For 5 triangles: 15 matches
- For 6 triangles: 18 matches

Notice:
6 − 3 = 3
9 − 6 = 3
12 − 9 = 3
…and so on.

Each time we add one more triangle, we need 3 more matches.
Why? Because the triangles are connected side-by-side — they share one side. So a new triangle only needs 2 new sides (2 matches) plus 1 shared side (already counted), but actually, in this pattern, it’s built so that each new triangle adds exactly 3 matches total — meaning they’re likely drawn separately or arranged without sharing sides (as shown by the picture: separate triangles). So each triangle uses 3 matches, no sharing.

So:
Number of matches = 3 × number of triangles.

That’s the pattern.