Question

Without adding, find the sum of 1 + 3 + 5 + 7 + 9 + 11.
[2 marks]

Answer 1

Given the sum of consecutive odd numbers is 1 + 3 + 5 + 7 + 9 + 11.
We know that, Sum of first $n$ odd numbers is $n^2$.
[1 mark]
Number of consecutive odd numbers = 6
Thus, $n$ = 6
Therefore, sum = $n^2$ = 6${}^2$ = 36
[1 mark]