A big rectangle is made up of 81 small rectangles. After removing some small rectangles from the big rectangle, the adjoining figure is obtained. The length of a small rectangle is 3 cm and its breadth is 2 cm. Find the total area of the rectangles removed.
A 81 sq. cm
B 114 sq. cm
C 129 sq. cm
D 90 sq. cm
Couldn't understand this question. Can you please explain how is it 19 rectangles removed