What is the sum of odd numbers from 28 to 78? Here we will show you step-by-step how to calculate the sum of odd numbers from 28 to 78.
Step 1) We start by finding the first (F) and last (L) odd numbers from 28 to 78. It is easy to do that by simply looking at the numbers. The first odd number is 29, and the last odd number is 77.
F = 29
L = 77
Step 2) Next, we calculate the total odd numbers (T) there are from 28 to 78, using a formula. Here is the formula and the math:
T = (L - F + 2) ÷ 2
T = (77 - 29 + 2) ÷ 2
T = 50 ÷ 2
T = 25
Step 3) Finally, we use the information from Step 1 and Step 2, and another formula, to calculate the sum of odd numbers from 28 to 78, like this:
Sum = (T ÷ 2) × (2 × F + (2 × (T - 1))
Sum = (25 ÷ 2) × (2 × 29 + (2 × (25 - 1))
Sum = 12.5 × (58 + 48)
Sum = 12.5 × 106
Sum = 1325
Sum of odd numbers from 28 to 78 = 1325
Sum of Odd Numbers Calculator
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