What is a Geometric Progression?

In this video you are shown what a geometric progression is, the formulae used along with an example.

Geometric Progression / Series : ExamSolutions - youtube Video

Example on finding the 1st term, common ratio and sum

This is a typical example where you are given terms in a geometric progression and asked to find the first term, common ratio and the sum of a certain number of terms.

  1. If the 6th term of a geometric series is 972 and the 9th term is 26244.
    Find the 1st term, the common ratio and the sum of the first 10 terms.
Geometric Series / Sequence : Example (1) : ExamSolutions - youtube Video

Example on Consecutive Terms

Questions involving consecutive terms can be easily worked out if you set up a ratio equation between the terms as the video shows.

  1. If 2x + 5, 6x – 10 and 8x + 20 are consecutive terms in a geometric series. Find the possible values of x and the corresponding terms.
Geometric Series / Sequence : Example (2) : ExamSolutions - youtube Video

Example on Investing

In this example I show you how the geometric progression can be used in an investment style problem. These problems can be quite tricky but worth learning.

  1. A girl invests £500 at the start of each year in an account paying 3.5% interest per year. At the start of each year he puts in another £500. After how many years has his account accumulated more than £20,000?
Geometric Series - How to handle Investment style problems : ExamSolutions Maths Revision - youtube Video