Triangle from sticks

Bob the boulder has many sticks of lengths 3.5 and 7. He wants to form triangles, each of whose edges consists of exactly one stick. How many non-congruent triangles can be formed with the sticks?

Correct answer:

n =  9

Step-by-step explanation:

$$\begin{gathered} 3+3<7 \\ 3-3-3 \\ 3-3-5 \\ 3-5-5 \\ 3-5-7 \\ 3-7-7 \\ 5-5-5 \\ 5-5-7 \\ 5-7-7 \\ 7-7-7 \\ n=9 \end{gathered}$$

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