# How do you find the sum of the infinite geometric series 72 + 12 + 2 + +… ?

##### 2 Answers

#### Explanation:

The formula for the sum of an infinite series is

where r is the common ratio and a is the first term.

Therefore,

First, you must find the common ratio, r, of the series.

#### Explanation:

r =

r =

r =

The sum is

Below I have posted one problem for your practice.

- Find the wanted information.

a) An infinite geometric series has a third term of 18 and a common ratio of

b) A pendulum has a first swing of 186 centimeters and a second swing of 124 centimetres. Assuming the pendulum swings forever, find the total distance travelled, rounded to the closest hundredth when necessary.