Question

There are 12 points in a plane . The number of straight lines joining any two of them when 3 of them are collinear

Answer 1

Answer:

There are 12 points in a plane, the no. of lines joining any two of them is given by

12C2 which is equal to 66

But 3 of them are collinear so we consider them as a single line

Total no. of lines=66-3+1=64