What is the sum of odd numbers from 20 to 161? Here we will show you step-by-step how to calculate the sum of odd numbers from 20 to 161.
Step 1) We start by finding the first (F) and last (L) odd numbers from 20 to 161. It is easy to do that by simply looking at the numbers. The first odd number is 21, and the last odd number is 161.
F = 21
L = 161
Step 2) Next, we calculate the total odd numbers (T) there are from 20 to 161, using a formula. Here is the formula and the math:
T = (L - F + 2) ÷ 2
T = (161 - 21 + 2) ÷ 2
T = 142 ÷ 2
T = 71
Step 3) Finally, we use the information from Step 1 and Step 2, and another formula, to calculate the sum of odd numbers from 20 to 161, like this:
Sum = (T ÷ 2) × (2 × F + (2 × (T - 1))
Sum = (71 ÷ 2) × (2 × 21 + (2 × (71 - 1))
Sum = 35.5 × (42 + 140)
Sum = 35.5 × 182
Sum = 6461
Sum of odd numbers from 20 to 161 = 6461
Sum of Odd Numbers Calculator
Please use the tool below to calculate the sum of odd numbers for another set of numbers.