Finding factors and multiples

This lesson develops the concept of ‘Greatest Common Factor’ (GCF) and ‘Least Common Multiple’ (LCM). The central theme is to separate out the two concepts.

There is an introductory ‘guess my numbers’ activity. The GCF and LCM of a pair of numbers is given and students must work out what the numbers are, saying if the solution is unique or if there might be other solutions. Student work is shown for peer assessment and features a range of methods, including placing prime factors on a Venn diagram.

There then follows a collaborative activity where a two way table for GCF and LCM is shown with some entries made. Students must work out the remaining values in the table. 

There are pre-lesson and post-lesson formative assessment tasks. Detailed teacher notes give suggestions on questioning and how to use the resources. Full solutions are given for each of the sections.

This is a concept development lesson from the Mathematics Assessment Resource Service, a collaboration between UC Berkeley and the Shell Centre team at the University of Nottingham. Further information on the collection is given here.