Mark the correct alternative in the following:

There are 10 points in a plane and 4 of them are collinear. The number of straight lines joining any two of them is


Number of straight lines formed by joining the 10 points if we take 2 points at a time = 10C2



Number of straight lines formed by joining the 4 points if we take 2 points at a time = 4C2



But, 4 collinear points, when joined in pairs give only one line.


Required number of straight lines =


45 – 6 + 1


= 40

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