Maths Dictionary · SS 2
Common ratio
Simple meaning
The fixed number you multiply by each time in a geometric progression.
Example
In 3, 6, 12, 24, … the common ratio r = 2.
See it
From the Geometric Progression lesson. Try moving things around.
Each bar = the bar before × 3
T4 = a × r3 = 2 × 33 = 2 × 27 = 54
Sum of the first 4 terms: S4 = 80
Term number n4
First term a2
Common ratio r3