Buying chips and candy

This resource features a task that explores setting up and solving simultaneous equations in a practical context.

Ralph and Jody go to a shop to buy potato chips and candy bars. Each buys a different combination of the items, with the total cost to each person being given. One equation is given, and students must explain each element of it. Students then derive the second equation from the information given in the task. Given that one of the coefficients differs by one, it is possible to solve the simultaneous equations through both informal and formal methods.

A full rubric is given for the task, together with examples of student work. The student work has scores given, together with suggestions for questions to address misconceptions.

This task is from the Mathematics Assessment Resource Service, a collaboration between UC Berkeley and the Shell Centre team at the University of Nottingham. A full rubric is given for the task, together with examples of student work and suggestions for helping students overcome misconceptions. Further information on the collection is given here.