Question

Without adding, find the sum:
1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23

Answer 1

The sum of first n odd numbers = $n^2$
In the expression: 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23, the number of terms (n) is eleven.
Hence, $n^2$ = 121, which is the required sum.