The question is from Permutation and Combination. This question is about Forming Triangles. Our task is to find out the number of triangles that can be formed from some points. This section hosts a number of questions which are on par with CAT questions in difficulty on CAT Permutation and Combination, and CAT Probability.
Question 28: Of 22 points on a plane, 8 are on a straight line, 7 are on another straight line and 10 are on a third straight line. How many triangles can be drawn by connecting some three points from these 22?
From the 22 points on a plane we can form 22C3 triangles but it is given that 8 are on one straight line, 7 are on another straight line and 10 more are on another straight line, so we can form triangles on joining points which are on straight lines
so we have to subtract (8C3+ 7C3 +10C3) from the total.
Hence, we can form 22C3 - (8C3+ 7C3 +10C3) triangles.
The question is "How many triangles can be drawn by connecting some three points from these 22?"
Choice B is the correct answer.
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