Without doing the actual addition, find the sum of: 1 \+ 3 \+ 5 \+ 7 \+ 9 \+ 11 \+ 13 \+ 15 \+ 17 \+ 19 \+ 21 \+ 23

As we know that, the sum of first n odd natural numbers = n 2 . Hence, 1 \+ 3 \+ 5 \+ 7 \+ 9 \+ 11 \+ 13 \+ 15 \+ 17 \+ 19 \+ 21 \+ 23 = 144.