Unit 2, Lesson 21-- Deriving the 9s Facts

Lesson 21-- Deriving the 9s Facts

Introduction

Hello Mathematicians! Today we will continue to work on fluently multiplying and dividing.  Take a look at this image.

ten packs of batteries, 5 in each pack

In your math notebook, answer these questions:

  • There are 10 packs of batteries with 6 in each pack.  How many total batteries is that? 
  • What multiplication equation represents 10 groups of 6?

Now what if used a pack of batteries, and now we only had 9 packs of batteries?

9 packs of batteries, 5 in each pack

  • What equation can we write to show that we started with 10 groups of 6 and then removed a group?
  • How many batteries are there now?

Video

Assignment

Directions:

  • Draw the chart below in your math notebook.
  • Create your own multiplication story that shows items that come in groups of 9. Draw a picture, write a story problem, and model
    the equation with a number line.

In Your Math Notebook:

Let’s get out our math journals and  work through the following application problem. Make sure you read the problem carefully, draw a picture to match your thinking and write and solve an equation.

Read, Draw, Write. DONE!

R (Read the problem carefully.)

Henry made 9 pizzas. He used 6 ounces of cheese for each pizza. How many ounces of cheese were used in all?

D (Draw a picture.)

W (Write and solve an equation.)

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Georgia Department of Education, Math