- The mathematical symbol is the capital letter S in Greek alphabet. It is used as the symbol for the sum of a series.

- Note that the last value you substitute is not always giving the number of terms that will be added.
**The number of terms = Top – Bottom + 1**- What is the number of terms in this series?
- The answer will therefore be:
**20 – 3 + 1 = 18**, so we will calculate the sum of 18 terms in the series.

**Infinite geometric series**

- A Geometric series can also have smaller and smaller values.
- What happens when .
- Therefore the series will converge to a number referred to as the
**sum to infinity**. This is the case only if -1 < r < 1 - Example: 9; 3; 1…
- therefore: the series converges and the sum to infinity exists

**Formula for sum to infinity**

**Activity **

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