There are 12 points in a plane, out of which 3 points are collinear. How many straight lines can be drawn by joining any two of them?
To get a straight line we just need to join two points. There are 12 numbers of points. Therefore, there is 12C2 = 66 number of straight lines. Among the 12 points, there are 3 points which are collinear. That means joining those 3 lines give a single straight line. That means the real number of straight lines present in the table is = (66 – 3C2 + 1) = (66 – 3 + 1) = 64.