For example, the series, 5, 6, 7, 8, 9 is a series and so is 17, 19, 21, 23, 25. You wouldn’t be able to use 5, 6, 9, 11, 14 because the progression isn’t constant.
For example, if you’re trying to add all of the integers from 1 to 100, n{\displaystyle n} will be 100 because it’s the largest integer in the sequence. As a reminder, integers are whole numbers, so n{\displaystyle n} cannot be a decimal, fraction, or negative number.
If you’re adding the first integers from 1 to 12, you’ll have 12 plus 1 to equal 13 terms.
For example, if you’re finding the sum of the integers from 1 to 100 exclusively, subtract 1 from 100 to get 99.
For example, if you’re summing the first 100 integers, plug 100 into n{\displaystyle n} to get 100∗(100+1)/2. If you’re finding the first 20 integers, use 20 for n{\displaystyle n}. Work 20∗(20+1)/2 to get 420/2. Your answer will be 210.
For example, if the problem asks you to find the sum of even integers from 1 to 20, use 20 as n{\displaystyle n}. Your formula will be 20∗22/4.
For example, to add the odd integers from 1 to 9, add 1 to 9. The equation will now look like 10∗(10)/4. Once you’ve worked the equation, you’ll get 10∗(10)/4 to equal 25.
For the example of consecutive formula 100∗101/2, multiply 100 by 101 to get 10100. Divide this by 2 to get an answer of 5050. For the example of even integers 20∗22/4, multiply 20 by 22 to get 440. Divide this by 4 to get a result of 110.
