PMC 2014-15 Q10
You can drag the red dot to change the shape of this rectangle and can click on each square to colour it.
Suppose all squares cut by the diagonal line are coloured, find the number of coloured squares for rectangles of the following dimensions.
(a) 9 cm by 5 cm
(b) 12 cm by 8 cm
(c) 168 cm by 72 cm