Question:
A mason has made a concrete slab. He needs it to be rectangular. In what different ways can he make sure that it is rectangular?
Solution:
(i) By measuring each angle - Each angle of a rectangle is $90^{\circ} .$
(ii) By measuring the length of the diagonals - Diagonals of a rectangle are equal.
(iii) By measuring the sides of rectangle - Each pair of opposite sides are equal.