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A geometric series has the same ratio between the consecutive numbers. An example explains it much better. Let us say that the first number in the series is 20 and the common ratio is 2; then the series is:
20, 40, 80, 160, 320, 640, ….
Starting from 20 and ratio 0.5, the series will be:
20, 10, 5, 2.5, 1.25, ….
So, the series starting from the number a and common ratio r is:
a, ar, ar^2, ar^3, ar^4, …
The sum of the series can be calculated by a simple formula which can be remembered easily. For the sum of the first n-elements in the series we have:
a+ar+ar^2+...+ar^{n-1} = a(r^n-1)/(r-1)
An interesting thing happens when r
About the author:
I started investing in December 2009and my first stock CreditSuisse (CS) tanked to almost half its
value. This nudged me to start learning about investing from the ground
up. I am a long term value investor and am planning to generate sustainable amount of money from investment income by the time I am 40 years old i.e., 2025.
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