What is the sum of odd numbers from 20 to 141? Here we will show you step-by-step how to calculate the sum of odd numbers from 20 to 141.
Step 1) We start by finding the first (F) and last (L) odd numbers from 20 to 141. It is easy to do that by simply looking at the numbers. The first odd number is 21, and the last odd number is 141.
F = 21
L = 141
Step 2) Next, we calculate the total odd numbers (T) there are from 20 to 141, using a formula. Here is the formula and the math:
T = (L - F + 2) ÷ 2
T = (141 - 21 + 2) ÷ 2
T = 122 ÷ 2
T = 61
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 141, like this:
Sum = (T ÷ 2) × (2 × F + (2 × (T - 1))
Sum = (61 ÷ 2) × (2 × 21 + (2 × (61 - 1))
Sum = 30.5 × (42 + 120)
Sum = 30.5 × 162
Sum = 4941
Sum of odd numbers from 20 to 141 = 4941
Sum of Odd Numbers Calculator
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