(i) The fee charged from a student every month by a school for the whole session is
400, 400, 400, 400, …
which from an AP, with common difference , d = 400 – 400 = 0
(ii) The fee charged month by a school from I to XII is
250, 250 + 50, 250 + 50(2), 250 + 50(3)………
250, 300, 350, 400……
Which from an AP, with common difference d = 300 – 250 = 50
= 100t
So, the amount of money in the account of Varun at the end of every year is
1000, (1000 + 100 × 1), (1000 + 100 × 2), (1000 + 100 × 3), …
i.e., 1000, 1100, 1200, 1300, …
which form an AP, with common difference , d = 1100 – 1000 = 100
(iv) Let the number of bacteria in a certain food = x
Since, they double in every second.
x, 2x, 4x, 6x . . . . .
a2 - a1 = 2x - x = x
a3 - a1 = 4x - 2x = 2x
Since, the difference between each successive term is not same. So, the list does form an AP.