One thing that I learned this week in Pre Calc 11 is how to find the number of terms in an Arithmetic Series, when the number of terms is unknown. An Arithmetic Series is the sum of terms in an Arithmetic Sequence. To find the number of terms in an Arithmetic Series you must use the first and last number of the series and the common difference in the sequence. For instance if this was my Arithmetic Series, 3+7+11+15…+43, then I would use those numbers and the equation = to fiqure out how many terms are in the series. I would replace with the first number in the series 3, (d) with the number 4 as my common difference and with the final number of the series 43. From there I will be able to solve the equation and figure out what n=? (n= the number of terms). Once I have the number of terms I can then find out the sum of the numbers in the series.

Below is an example showing the steps I would take and the equations I would use to find the number of terms in an Arithmetic Series.