Unpicking the workings of a numerical trick allows students to put their algebra skills to use in this free GCSE algebra lesson plan…
To many students, GCSE algebra is a morass of letters, numbers and symbols which they have to manipulate according to arbitrary and pointless rules to obtain a ‘correct answer’ which has no meaning or importance outside of the question.
In this lesson, students use algebra to make sense of a number trick that you, the teacher, perform. Students will explore the mechanics and experiment with some numbers. They’ll then use algebra to try to probe exactly how and why the trick works.
It’s easy to check the rule on a few numerical examples by working them out. However, a short piece of algebra helps students to see what is going on under the surface.
This GCSE algebra lesson provides an opportunity to work on expanding brackets and simplifying algebraic expressions. You’ll also make sense of the final answer in terms of the place value of the original numbers.
Why teach this GCSE algebra lesson plan?
Students often like to see ‘tricks’ or ‘cheats’ for calculation. It is even better if these can be used to stimulate their curiosity about why they work and provide an opportunity for algebra to reveal the answer.
Colin Foster is an assistant professor in mathematics education in the School of Education at the University of Nottingham. He has written many books and articles for mathematics teachers. Discover more KS4 maths lesson plans from Colin Foster.
