+

Multiplying Fractions by Whole Numbers5th Grade MathematicsAmber Wiley

+Objectives Students will be able to:

Use repeated addition to multiply a fraction by a whole number

Use a model to multiply a fraction by a whole number

Fluently multiply fractions by whole numbers using the repeated addition and model method

+Pre-Assessment Activity

Solve the following problem using repeated addition. Use the pen tool to circle your final answer.

½ x 3

Solve the following problem using a model. Use the pen tool to create a circle for your model, and use the highlighter to shade in the correct amounts. Circle your final answer.

⅗ x 4

+Time to Check!Use your hand up/hand down tool to let me know if you got the answer correct! Let’s see!

Repeated Addition Method:

½x 3= ½+½+½=3/2

Raise your hand if you got this correct!

+Time to Check! This time, use the green check to tell me if you got this correct, or the red x to let me know if you got it incorrect. Let’s check!

Model Method:

⅗ x 4

+ + + = 12/5

+Introduction

To introduce the topic, you will watch the following video. Be prepared to answer the following questions in your chat box when it is over!

Multiplying Fractions by Whole Numbers

1. What are the three methods that this video discusses when multiplying fractions by whole numbers?

2. Which two methods are we going to discuss today?

3. Which method do you think will be the easiest for you and why?

*Type your answer in the chat box now and share with your classmates!

+Multiplying Using Repeated AdditionKeep in mind that multiplying is the same as repeated

addition, so ⅖ x 6 is the same thing as adding ⅖ six times. Check it out:

⅖+⅖+⅖+⅖+⅖+⅖=12/5Notice we added all of the numerators together and kept

the denominator the same. Remember: you never change the denominator when you add or subtract fractions!

+Multiplying Using Repeated AdditionNow it is your turn to try! Solve the

following problem on a piece of paper using repeated addition, and when I give the cue, say your answer one at a time into the microphone.

⅛ x 9 =

+Time to Check!Now that everyone has shared their answer over the microphone, look at the correct way to solve this problem. Place an emoticon next to the answer if you got it correct!

⅛+⅛+⅛+⅛+⅛+⅛+⅛+⅛+⅛= 9/8

Explanation: ⅛x9 is the same thing as adding ⅛ nine times. When you add ⅛ nine times, you get 9/8!

+Multiplying Using Models

Suppose I give you the multiplication problem ¼x 5. This is the same thing as saying 5 groups of ¼. Let’s model this.1 2 3 4 5

5 parts, or 5/4, are shaded. So, the product of ¼x 5 is 5/4. The denominator is how many parts each circle is broken Into. Do NOT add up the total number of parts and make ityour denominator!

+Multiplying Using ModelsNow it is your turn to try! Use the pen tool to create your models to represent the problem. Then, use the highlighter tool to highlight the correct fraction into your model.

⅚ x 2=

+Time to Check!If you got the correct answer, please click on the green check. If you answered incorrectly, please click on the red x.

⅚ x 2

1 2

10 parts, or 10/6, are shaded. So the product of ⅚x2 is 10/6.

+PracticeUsing a separate piece of paper, practice multiplying fractions by a whole number using the repeated addition method. Use the line tool to match the problem to its correct product.

⅞ x 3 6/2⅕x4 6/4½x6 4/5¾x2 21/8

+PracticeUsing a separate piece of paper, multiply the following fraction and whole number. Use your pointer tool to point to the model that correctly represents the multiplication problem.

⅝ x 6

=

=

=

30/48

30/8

25/8

+Test Your Knowledge!

Use the link to go to a practice page. Complete ten practice problems. You need to use repeated addition for five problems, and models for the last five problems. Please let me know how many you get correct out of ten!

Practice

+Post-AssessmentComplete the two problems below. You must use repeated addition to complete the first problem, and models to complete the second. Use the pen and highlighter tool to show your work.

1. ⅛ x 3

2. ⅔ x 4

+Extension ActivityAnswer the following questions in your chat box. Then, create a problem of your own and send it to someone in the class to solve. Let them know which method to use to solve it. Everyone must solve a problem, so you may not to send it to a person that already has a question to solve. Send your answers, along with the problem given to you, in the chat box, as well! Good luck!

1. Which method do you like using better? Why?

2. What is the most difficult part of solving these problems?

3. What is the easiest part of solving these problems?

4. Create your own problem and send it to someone in class. When you receive your problem, complete it and send the answer, along with the problem, in the chat box!