What is the sum of the first 22 odd numbers?

Answer 1

The sum of a sequence is given by sum = n/2(2a + (n-1)d) where:

n = how many

a = first number of sequence

d = difference between terms of sequence.

For the first 22 odd numbers these are:

n = 22

a = 1

d = 2

→ sum = 22/2(2×1 + (22 - 1)×2)) = 22² = 484

The sum of the first n odd numbers is always n²:

sum = n/2(2×1 + (n-1)2) = n/2(1 + (n-1))×2 = n(n) = n²

Answer 2

You can either add them up - Excel can help you there - or use the formula for the sum of an arithmetic series.