M3 L15 Powerpoint

1. Multiplication and Division Using
Units of 9
Module 3: Lesson 15
Objective: Interpret the unknown in multiplication
and division to model and solve problems.

2. Multiply by 9 (7 minutes)
6 x 9 =
Let’s skip count by nines to find the answer. I will raise a finger for
each nine.
Let’s see how we can skip-count down to find the answer too. Start
at 90.
Let’s skip count up again to find the answer, but this time start at
45.
Repeat the process for 8 x 9, 7 x 9, and 9 x 9

3. Multiply by 9 (7 minutes)
Let’s practice multiplying by 9. Be sure to work
left to right across the page

4. Group Counting (4 minutes)
Sixes to 60
Sevens to 70
Eights to 80

5. Divide by 9
(4 minutes)
a x 9 = 18
Write the value of a.
18 ÷ 9 =
Say the division sentence.
Continue with the following possible sequence:
b x 9 = 45, c x 9 = 36, d x 9 = 54, e x 9 = 27, f x 9 = 90, g x 9 = 81,
h x 9 = 72

6. Concept Development
(35 minutes)
Problem 1: Interpret the unknown in
multiplication.
Ada buys 9 packs of highlighters with 4 in each pack.
After giving 1 highlighter to each classmate, she has 17
left. How many highlighters did Ada give away?
Write an equation to find the total number of
highlighters. Instead of using a question mark, use
letter h to represent the unknown.

7. What equation did you use?
What strategy for solving nines facts did you use?
What is the value of h?
How many highlighters did Ada have at the start?
Is the problem complete yet?
Solve the second step of the problem using letter g to represent the
unknown.
What is the value of g?
How many highlighter did Ada give away? Can we tell how many
classmates Ada has? How do you know?

9. Concept Development
(35 minutes)
Problem 2: Interpret the unknown in division.
Eliza finds a bag of 72 marbles and runs to share them with 8 of her
friends. She’s so excited that she drops the bag and loses 18 marbles.
How many marbles will Eliza and each of her friends get?
Model the problem. How many units are in your model?
What part of the problem tells you that your model needs 9 units?
What should we do first, subtract or divide? Why?
Write an equation to solve for the first unknown. Use m to represent the
number of marbles Eliza has.

10. Concept Development
(35 minutes)
What is the value of m?
So how many marbles does Eliza have to give away?
Is our work on this problem finished?
Complete your model and write an equation to solve for the second
unknown. Use g to represent the number of marbles each friend gets.
How many marbles does each friend get? How do you know?

11. Problem Set (10 minutes)
Student Debrief (10 minutes)
Exit Ticket (3 minutes)

12. Homework
3-3 Lesson 15
Homework
Is Due Tomorrow!