(Q). Find the number of rectangles in a chess board of 11×11 grid instead of 8×8 grid.
Solution:-
Chess board has 11 + 1 = 12 set of parallel lines & another set of 11 + 1 = 12 set of parallel lines.
Hence number of rectangle = ¹²C₂ × ¹²C₂
= 66 × 66
= 4356 Answer
