The sides AB, BC, and CA of a triangle ABC have 3, 4, and 5 interior points, respectively, on them. The number of triangles that can be constructed using these interior points as vertices is ___.
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Solution
We have total 3+4+5 = 12 points. So, number of Δs that can be formed using 12 such points is given by Total number of ways of selecting three point - Number of ways three collinear points are selected =12C3−3C3−4C3−5C3=12×11×106−1−5×42×1=220−15=205