What is the sum of odd numbers from 6 to 20? Here we will show you step-by-step how to calculate the sum of odd numbers from 6 to 20.
Step 1) We start by finding the first (F) and last (L) odd numbers from 6 to 20. It is easy to do that by simply looking at the numbers. The first odd number is 7, and the last odd number is 19.
F = 7
L = 19
Step 2) Next, we calculate the total odd numbers (T) there are from 6 to 20, using a formula. Here is the formula and the math:
T = (L - F + 2) ÷ 2
T = (19 - 7 + 2) ÷ 2
T = 14 ÷ 2
T = 7
Step 3) Finally, we use the information from Step 1 and Step 2, and another formula, to calculate the sum of odd numbers from 6 to 20, like this:
Sum = (T ÷ 2) × (2 × F + (2 × (T - 1))
Sum = (7 ÷ 2) × (2 × 7 + (2 × (7 - 1))
Sum = 3.5 × (14 + 12)
Sum = 3.5 × 26
Sum = 91
Sum of odd numbers from 6 to 20 = 91
Sum of Odd Numbers Calculator
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