What is the sum of odd numbers from 11 to 28? Here we will show you step-by-step how to calculate the sum of odd numbers from 11 to 28.
Step 1) We start by finding the first (F) and last (L) odd numbers from 11 to 28. It is easy to do that by simply looking at the numbers. The first odd number is 11, and the last odd number is 27.
F = 11
L = 27
Step 2) Next, we calculate the total odd numbers (T) there are from 11 to 28, using a formula. Here is the formula and the math:
T = (L - F + 2) ÷ 2
T = (27 - 11 + 2) ÷ 2
T = 18 ÷ 2
T = 9
Step 3) Finally, we use the information from Step 1 and Step 2, and another formula, to calculate the sum of odd numbers from 11 to 28, like this:
Sum = (T ÷ 2) × (2 × F + (2 × (T - 1))
Sum = (9 ÷ 2) × (2 × 11 + (2 × (9 - 1))
Sum = 4.5 × (22 + 16)
Sum = 4.5 × 38
Sum = 171
Sum of odd numbers from 11 to 28 = 171
Sum of Odd Numbers Calculator
Please use the tool below to calculate the sum of odd numbers for another set of numbers.