How To Work Out The Sum To Infinity Of A Geometric Sequence, (Common Ratio Between -1 and 1)

In this video you will be shown how to work out the sum to infinity of a geometric number sequence. To do this use the formula S=a/1-r. Where a is the first number of the number sequence and r is the common ratio. The common ration can be found by dividing the second term by the first term.

So in example 1 the geometric number sequence is 12,6,3… and you are asked to find the sum to infinity. The first term of the sequence is 12 and the common ratio is 1/2 (6/12). So you can now substitute these into the formula to give 12/(1-1/2) which gives an answer of 24. So the sum to infinity is 24.