Identify the common difference of the given AP: a, a+d, a+2d, a+3d, ...
Find the common difference (d) in the following APs respectively.
(i) 20, 40, 60, 80, 100,..
(ii) 5, 0, -5, -10, -15, ...
(iii) 2, 2, 2, 2, 2..