IB Math AA SL 1.3 - Geometric Sequences

This IB Math AA SL 1.3 – Geometric Sequences slide deck introduces students to growth patterns driven by multiplicative change, helping them distinguish geometric sequences from other types of numerical patterns. Beginning with clear examples such as a doubling sequence, the presentation explains how dividing consecutive terms allows students to verify the existence of a common ratio, forming the basis for identifying and analyzing geometric behavior.

The lesson progresses into formal notation, presenting the formula for the nth term of a geometric sequence and guiding learners through determining unknowns, including the first term, the common ratio, or the value of n, by strategically applying the formula to known values. Worked examples model the logic of comparing ratios and solving equations, reinforcing reasoning skills crucial to IB-style assessment.

Students then expand their understanding to geometric series, learning how to calculate the sum of a finite geometric sequence using structured formulas. Special attention is given to interpreting when and how the IB may require students to solve for n, often considered the most challenging type of geometric sequence question. The deck provides tips, visual guidance, and strategic approaches that support success in these higher-demand problem types.

A relatable, real-world marathon training problem bridges theory and application: students compare arithmetic growth (Andrew) and geometric growth (Steven) to determine distances run on specific days and identify when one sequence first surpasses another. Use of graphical calculator methods is included, developing computational fluency and modeling skills consistent with IB expectations.

With visual clarity, structured examples, calculator integration, and step-by-step problem solving, this slide deck supports classroom teaching, independent study, and exam revision alike. It equips SL students with both formula mastery and interpretation skills needed to approach multiplicative growth confidently across mathematical and applied contexts.