Find the maximum number of points of intersection of 5 circles and 8 straight lines.
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This is the same reasoning as Puneet Sharma's answer, just using LaTeX to make it visually clearer
2 circles intersect each other at most 2 times. The number of circle intersections is equal to 2 times the number of circle pairs, 2 × ( 2 5 ) = 2 × 1 0 = 2 0
2 lines intersect each other at most 1 time. The number of line intersections is equal to 1 times the number of line pairs, 1 × ( 2 8 ) = 1 × 2 8 = 2 8
Lastly, a line and a circle intersect at most 2 times. The number of line and circle intersections is equal to 2 times the number of line and circle pairs, 2 × 5 × 8 = 8 0
2 0 + 2 8 + 8 0 = 1 2 8
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If you select any two circles, you can have max 2 points of intersection. =(5c2)(2). If u select any two straight lines then you have max one point of intersection =( 8c2)(1). And if u select one circle and one straight line you get max 2 points of intersection =(8c1)(5c1)(2). hence total points add up to 20 +28 + 80= 128