When I start the algebra on level 2 courses, I tend to kick off with substituting into formulas as a link back to the work on (what else?) BODMAS. I add in some of the less logical aspects of the way we write formulas and by bringing in substitution early, the idea of working out tables of values, and the need to work with directed numbers is fixed in the mind. This mini-lesson includes a _brief_ presentation on what substitution does, and then leads into a pairs activity designed to last about 20 minutes. At that point, a ‘traditional’ book exercise is used to fix ideas and provide examples of exam questions.

The pairs activity is based around two sets of cards – print them from the powerPoint files below using the ‘handout’ prining option with ‘6 slides to a page’ set.

* PowerPoint explaining substitution – about 10 minutes
* The formula cards
* The value cards

One players get a set of *formula cards*, and the other a set of *value cards*. The activity results in the result of each formula being calculated by substituting in the values from one or two ‘value’ cards. Students *record the formula, the values for X and Y and the result*.

The plenary has the students writing the X and Y values and the results on a *flipchart*, one for each formula. In this way a table of values can be constructed for each of the formulas. Comments and checking allow for *review* of directed numbers, sequence of operations, powers and indicies.