In a Plane there are 37 straight lines, of which 13 pass through the point A and

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Question
In a Plane there are 37 straight lines, of which 13 pass through the point A and 11 pass through the point B. Besides, no three lines pass through one point, no lines passes through both points A and B , and no two are parallel. Find the number of points of intersection of the straight lines.
Options
A. 525
B. 535
C. 545
D. 555

Correct Answer

535

Explanation

The number of points of intersection of 37 lines is $C_{2}^{37}$ . But 13 straight lines out of the given 37 straight lines pass through the same point A.

Therefore instead of getting $C_{2}^{13}$ points, we get only one point A. Similarly 11 straight lines out of the given 37 straight lines intersect at point B. Therefore instead of getting $C_{2}^{11}$ points, we get only one point B.