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Explore how to write multiplication equations using the distributive property. Practice breaking apart arrays, creating equations, and understanding the total product. Use visual models for better comprehension.
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Writing Equations Using the Distributive Property MAFS.3.OA.2.5
Lesson Opening • If you combined the arrays below, what multiplication equation could represent it? • If the two equations below were combined, what multiplication equation could represent it? (Use square tiles to model if needed) 2 × 5 = 10 2 × 5 = 10 2 × 3 2 × 3
Lesson Opening • If you combined the arrays below, what multiplication equation could represent it? • If the two equations below were combined, what multiplication equation could represent it? (Use square tiles to model if needed) 2 × 5 = 10 2 × 5 = 10 2 × 3 2 × 3 2 × 6 = 12 2 × 10 = 20 or 4 × 5 = 20
Yesterday, we learned… 3 × 2 3 × 2 3 × 4 can be broken apart
Yesterday, we learned… 3 × 2 3 × 2 3 × 4 can be broken apart Here is how we would write it as an equation: + 3 x 4 = (3 × 2) (3 × 2)
3 x 4 = (3 x 2) + (3 x 2) 3 x 2 3 x 2 Put parentheses around each multiplication array to show that it NAMES the array. Also, if we solve the equation we have to do the operation inside the parentheses first!
3 x 4 = (3 x 2) + (3 x 2) = 12 3 x 2 3 x 2 Then, put an addition sign in between the arrays to show that you ADD the products of the array to find the TOTAL product.
Write the equation for this array: 4 x 3 4 x 2 4 x 5 = (4 x 2) + (4 x 3)
Write the equation for this array: 4 x 3 4 x 2 4 x 5 = (4 x 2) + (4 x 3) 3 2 The 5 was decomposed into 2 and 3. Then each part was multiplied by 4.
Write the equation for this array: 3 x 5 6 x 5 = (3 x 5) + (3 x 5) = 30 3 3 x 5 3 The 6 was decomposed into 3 and 3. Then each part was multiplied by 5.
Here’s another way to think about it… 6 tens 4 2 4 tens 6 6 x 10 2 tens 2 x 10 4 x 10 This is a number bond that shows 6 decomposed into 4 and 2. This is a number bond that shows 6 tens decomposed into 4 tens and 2 tens. + 6 x 10 = (4 x 10) (2 x 10)
Let’s try another one. 7 fours 5 fours This is a number bond that shows 7 fours decomposed into 5 fours and 2 fours. 7 x 4 + 7 x 4 = (5 x 4) (2 x 4) 2 fours 2 x 4 5 x 4
On your dry-erase board, write an equation for the following: 8 threes 5 threes = 24 + 8 x 3 = (5 x 3) (3 x 3) 8 x 3 or + 8 x 3 = (4 x 3) (4 x 3) = 24 or 3 threes = 24 + 8 x 3 = (6 x 3) (2 x 3) 3 x 3 5 x 3 or + 8 x 3 = (7 x 3) (1 x 3) = 24
Use the Distributive Property to write an equation (think of a number bond or an array). (3 × 6) + (3 × 6) = 36 (4 × 6) + (2 × 6) = 36 (5 × 6) + (1 × 6) = 36 (6 × 3) + (6 × 3) = 36 (6 × 4) + (6 × 2) = 36 (6 × 5) + (6 × 1) = 36 6 × 6
Use the Distributive Property to write an equation (think of a number bond or an array). (5 × 8) + (2 × 8) = 56 (4 × 8) + (3 × 8) = 56 (6 × 8) + (1 × 8) = 56 (7 × 4) + (7 × 4) = 56 (7 × 5) + (7 × 3) = 56 (7 × 6) + (7 × 2) = 56 7 × 8
Your Turn • Draw the array that represents the multiplication expression. • Use two different colors to represent how you can break apart the array. • Write the equation that represents how you broke apart the array. • Don’t forget to write the product.
Bonus Questions • The following equation represents an array broken apart into 3 smaller arrays. What is the equation for the original array? How do you know? • Can you break apart this array into 3 smaller arrays? What would the equation be? (5 × 3) + (5 × 3) + (5 × 2) = 40 3 × 12
Bonus Questions • The following equation represents an array broken apart into 3 smaller arrays. What is the equation for the original array? How do you know? • Can you break apart this array into 3 smaller arrays? What would the equation be? rows columns rows rows columns columns (5 × 3) + (5 × 3) + (5 × 2) = 40 Since there are 5 rows in each of the arrays, I know the array has 5 rows. So then I add up all the columns. 3 + 3 + 2 = 8. So the original array is 5 × 8. 3 × 12
Are there other ways? Bonus Question #2 Answer 3 × 12 3 twelves 12 threes 12 threes Choose to decompose either the 3 or the 12. 4 threes 1 twelve 1 twelve 4 threes 10 threes 1 three 1 three 4 threes 1 twelve (10 x 3) + (1 x 3) + (1 x 3) = 36 (4 x 3) + (4 x 3) + (4 x 3) = 36 (1 x 12) + (1 x 12) + (1 x 12) = 36
Exit Ticket: Which expressions could represent the array? • 6 × 4 • 4 × 6 • (6 × 4) + (6 × 4) • (3 × 4) + (3 × 4) • (6 × 2) + (6 × 2) • (6 × 4) × (6 × 2)