What is the sum of odd numbers from 8 to 91? Here we will show you step-by-step how to calculate the sum of odd numbers from 8 to 91.
Step 1) We start by finding the first (F) and last (L) odd numbers from 8 to 91. It is easy to do that by simply looking at the numbers. The first odd number is 9, and the last odd number is 91.
F = 9
L = 91
Step 2) Next, we calculate the total odd numbers (T) there are from 8 to 91, using a formula. Here is the formula and the math:
T = (L - F + 2) ÷ 2
T = (91 - 9 + 2) ÷ 2
T = 84 ÷ 2
T = 42
Step 3) Finally, we use the information from Step 1 and Step 2, and another formula, to calculate the sum of odd numbers from 8 to 91, like this:
Sum = (T ÷ 2) × (2 × F + (2 × (T - 1))
Sum = (42 ÷ 2) × (2 × 9 + (2 × (42 - 1))
Sum = 21 × (18 + 82)
Sum = 21 × 100
Sum = 2100
Sum of odd numbers from 8 to 91 = 2100
Sum of Odd Numbers Calculator
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