Without adding find the sum

(i) 1 + 3 + 5 + 7 + 9

(ii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

(iii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23

We know that the sum of
first *n* odd natural numbers is *n*^{2}.

(i) Here, we have to find the sum of first five odd natural numbers.

Therefore,
1 + 3 + 5 + 7 + 9 = (5)^{2} = 25

(ii) Here, we have to find the sum of first ten odd natural numbers.

Therefore,
1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 = (10)^{2} = 100

(iii) Here, we have to find the sum of first twelve odd natural numbers.

Therefore,
1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 +17 + 19 + 21 + 23 = (12)^{2}
= 144

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