1.

How many triangles can be formed by joining the vertices of a pentagon?1). 102). 203). 304). 40

Answer»

LET the vertices of the PENTAGON be A1, A2, A3, A4 and A5.

One triangle is formed by selecting a GROUP of 3 points from the 5 given vertices.

⇒ Number of triangles = Number of groups of 3 each from 5 points

5C3 = 5!/{(5 - 3)! × 3!} = 10

∴ The number of triangles that can be formed by JOINING the vertices of a pentagon = 10


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