Math 1 · Lesson 1 · Identity and inverse

The Do-Nothing Numbers and Their Undo Partners

Two numbers change nothing. Two kinds of partners undo everything. Learn the math words and the plain English, then catch the hidden 1s and 0s in math you already do.

About 25 minutes Say the math word, then the plain English

The parts of this lesson

Each part is its own short page. Go in order, or pick the one you need.

1Warm-up: change nothing, undo everythingAnswer these four on paper before reading on.Start here 2The parallel: adding and multiplyingSay the math word first, then the plain English, every time. 3The one sentence to say out loudIf you remember nothing else, remember this one. 4Which one is it?For each statement, pick the property and the operation. 5The hunt for hidden 1s and 0sThree things you already know how to do. 6Practice ProblemsTry them, get help one step at a time, then print how it went.

Finn

Hi, I am Finn. I will be down here the whole way through.

Today is about four numbers. Two of them change nothing, and two of them undo everything. That is the entire lesson, so if you get those four, you are done.

When you reach the practice, press Hint any time you are stuck and I will tell you what I would look at first. Asking is not cheating.

Printables

The worksheet mirrors this page (Parts A to E, with an answer key). The lesson plan has the 25-minute timeline, the vocabulary table, and the misconceptions to listen for.

Worksheet and answer key (PDF) Lesson plan (PDF)

Where this goes next

Unit Rates practiceEvery rate problem there is solved by multiplying by a reciprocal to turn the time into 1. Same trick, new setting. Next lesson: Commute, Associate, DistributeThe properties are named after ordinary words. If you know the word, you know what the numbers are allowed to do. Back to the Math 1 mapEvery Math 1 lesson, in course order. Tell us what you thoughtA few quick questions about this lesson. It takes a minute, and it is how the lesson gets better.