We know that the sum of first n odd natural numbers is n2.
(i) 49 = 72 Therefore, 49 is the sum of first 7 odd natural numbers. 49 = 1 + 3 + 5 + 7 + 9 + 11 + 13
(ii) 121 = 112 Therefore, 121 is the sum of first 11 odd natural numbers. 121 = 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21