Encryption -- Solving One-step Equations

The purpose of the activity is to for students to internalize the idea of solving equations by using the inverse operation. Incidently, this is the same idea behind a lock, digital or physical. Anyone familiar with encoder rings will recognize their similarity to combination locks.

Students will learn the basics of a shift cypher and apply that knowledge to encrypting and decrypting messages. After the teacher has debriefed the activity, the class will apply their understanding of shift cyphers to solving one-step equations with the operation of addition.

Pre-planning:

30-60 minutes

Students grouped into pairs

scratch paper for each student

Prerequisite Knowledge:

use variables to represent an unknown value

add and subtract positive and negative integers

Learning Objectives:

solve equations through the process of inverting the operator

experience a relevant external application of solving equations: locking and unlocking

reinforce the idea of subtraction as adding an additive inverse