VIEWS: 2 PAGES: 44 POSTED ON: 1/21/2014
Multiplication Mrs. Walker 4th Grade Objective: Today will learn how to multiply numbers with 2 digits by numbers with 1 digit. Example: 34 x 9 Why do we need to know the Multiplication Properties? It helps you solve problems without working them out. It helps with mental math. It makes understanding math easier. Vocabulary To Know: Factor Product Commutative Property Associative Property Identity Property Zero Property Distributive Property Factor The numbers that are multiplied together in a multiplication problem. Example: 34 x 9 = 306 Product The answer to a multiplication problem. Example: 34 x 9 = 306 Commutative Property of Multiplication The order that factors (numbers) are multiplied will not change the product (answer). Example: 56 x 4 = 4 x 56 Commutative Property of Multiplication Lets Practice: 1. 34 x 8 = ____ x 34 2. 5 x ____ = 62 x 5 3. ____ x 9 = 9 x 71 Associative Property of Multiplication The way that factors (numbers) are grouped will not change the product (answer). Example: (21 x 3) x 9 = 21 x (3 x 9) Associative Property of Multiplication Lets Practice: 1. 34 x (___ x 6) = (34 x 8) x 6 2. (431 x 6) x 3 = ___ x (6 x 3) 3. 19 x (___ x ___) = (19 x 2) x 7 Zero Property of Multiplication Any factor (number) multiplied by 0 will equal 0. Example: 679 x 0 = 0 Zero Property of Multiplication Lets Practice: 1. 43 x 0 = ____ 2. 35 x ____ = 0 Identity Property of Multiplication Any factor (number) multiplied by 1 will equal that number. Example: 679 x 1 = 679 Identity Property of Multiplication Lets Practice: 1. 55 x 1 = ____ 2. 77 x ____ = 77 Distributive Property of Multiplication When two addends are multiplied by a factor the product will be the same as when each addend is multiplied by the factor and the products are added. Example: (2 + 3) x 4 = (2 x 4) + (3 x 4) Distributive Property of Multiplication Lets Practice: 1. (2 + 6) x 34 = (___ x 34) + (___ x 34) 2. (6 + 9) x 16 = (___ x 16) + (___ x 16) 3. (4 + 5) x 23 = (4 x ___) + (5 x ___) 4. (___ + 3) x 11 = (7 x 11) + (3 x 11) 5. (___ + ___) x 90 = (4 x 90) + (1 x 90) 2 Digit x 1 Digit Multiplication Steps 1. Write the problem – lining up the place values (ones under ones). 2. Multiply the bottom number in the ones place by the top number in the ones place. 3. Write the answer below the problem in the ones place. Regroup if necessary. 4. Multiply the bottom number in the ones place by the top number in the tens place and add the number you carried if you have one. 5. Write the answer below the problem in the tens place. 2 Digit x 1 Digit 2 1 Start Here 2 Digit x 1 Digit 1 1 2 2 1 5 6 0 Hand Trick: UP then OVER! 2 Digit x 1 Digit 1 6 3 2 1 4 2 5 2 Hand Trick: UP then OVER! 2 Digit x 1 Digit 6 9 9 2 1 7 6 9 3 Hand Trick: UP then OVER! You Try One… 2 8 4 2 1 6 5 0 4 You Try Another… 7 1 9 8 1 5 2 You Try Another… 3 1 9 2 7 9 3 Digit x 1 Digit 1 2 1 2 3 2 1 1 5 1, 0 6 0 3 Digit x 1 Digit 1 2 6 3 9 3 2 1 1 3 1, 9 1 7 2 & 3 Digit x 1 Digit Independent Practice 1. 14 x 5 = 6. 28 x 1 = 2. 62 x 2 = 7. 26 x 3 = 3. 234 x 9 = 8. 343 x 6 = 4. 45 x 7 = 9. 54 x 8 = 5. 87 x 4 = 10. 414 x 3 = 2 Digit x 2 Digit Steps Step 1: Write the problem making sure you line up the correct place values. 2 1 2 1 Step 2: Do the green Start Start Here steps first. Here Step 3: Mark out the number you carried and add a zero to hold 0 the ones place. Step 4: Do the red steps next. Step 5: Add the green and red answers together. Hand Trick: UP then OVER and OVER then UP! 1 2 Digit x 2 Digit 1 Step 1: Write the problem making sure 4 6 you line up the correct place values. 2 3 2 1 2 1 Step 2: Do the green steps first. Step 3: Mark out the 1 3 8 number you carried and add a zero to hold 0 the ones place. 9 2 Step 4: Do the red steps next. 1, 0 5 8 Step 5: Add the green and red answers together. Hand Trick: UP then OVER and OVER then UP! 2 Digit x 2 Digit 1 Step 1: Write the problem making sure 8 3 you line up the correct place values. 5 2 2 1 2 1 Step 2: Do the green steps first. 1 Step 3: Mark out the 1 6 6 number you carried and add a zero to hold 0 the ones place. 4 1 5 Step 4: Do the red steps next. 4, 3 1 6 Step 5: Add the green and red answers together. Hand Trick: UP then OVER and OVER then UP! 1 2 Digit x 2 Digit 3 Step 1: Write the problem making sure 9 4 you line up the correct place values. 3 8 Step 2: Do the green steps first. Step 3: Mark out the 1 7 5 2 number you carried and add a zero to hold 0 the ones place. 2 8 2 Step 4: Do the red steps next. 3, 5 7 2 Step 5: Add the green and red answers together. Hand Trick: UP then OVER and OVER then UP! 1 2 Digit x 2 Digit 2 Step 1: Write the problem making sure 8 5 you line up the correct place values. 2 5 Step 2: Do the green steps first. Step 3: Mark out the 1 4 2 5 number you carried and add a zero to hold 0 the ones place. 1 7 0 Step 4: Do the red steps next. 2, 1 2 5 Step 5: Add the green and red answers together. You try one… 1 Step 1: Write the problem making sure 2 3 you line up the correct place values. 1 4 Step 2: Do the green steps first. Step 3: Mark out the 1 9 2 number you carried and add a zero to hold 0 the ones place. 2 3 Step 4: Do the red steps next. 3 2 2 Step 5: Add the green and red answers together. 1 You try another… 2 Step 1: Write the problem making sure 7 3 you line up the correct place values. 4 8 Step 2: Do the green steps first. 1 Step 3: Mark out the 1 5 8 4 number you carried and add a zero to hold 0 the ones place. 2 9 2 Step 4: Do the red steps next. 3, 5 0 4 Step 5: Add the green and red answers together. 2 Digit x 2 Digit Independent Practice 1. 26 x 35 = 6. 28 x 12 = 2. 62 x 41 = 7. 26 x 37 = 3. 34 x 99 = 8. 43 x 62 = 4. 45 x 74 = 9. 54 x 86 = 5. 87 x 73 = 10. 44 x 38 = 3 Digit x 2 Digit What do you think the steps will be to multiply a 3 Digit x a 2 Digit? 548 423 937 x 19 x 25 x 62 Great Job!