Course Mental Math 1-5 Mental Math Course 1 Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day

Course Mental Math Warm Up Find each sum or product (24) 4. 7(12) 5. 3(91) 6. 6(15)

Course Mental Math Problem of the Day Determine the secret number from the following clues: The number is a multiple of 5. It is divisible by 3. It is less than 200. Its tens digit equals the sum of its other two digits. 165

Course Mental Math Learn to use number properties to compute mentally.

Course Mental Math Vocabulary Commutative Property Associative Property Distributive Property

Course Mental Math Mental math means “doing math in your head.” Many mental math strategies use number properties that you already know.

Course Mental Math COMMUTATIVE PROPERTY (Ordering) WordsNumbers You can add or multiply numbers in any order =  2 = 2  15

Course Mental Math ASSOCIATIVE PROPERTY (Grouping) WordsNumbers When you are only adding or only multiplying, you can group any of the numbers together. (17 + 2) + 9 = 17 + (2 + 9) (12  2)  4 = 12  (2  4)

Course Mental Math Additional Example 1A: Using Properties to Add and Multiply Whole Numbers Evaluate Look for sums that are multiples of Use the Commutative Property (17 + 3) + (5 + 15) Use mental math to add Use the Associative Property to make groups of compatible numbers.

Course Mental Math Additional Example 1B: Using Properties to Add and Multiply Whole Numbers Evaluate 4  13  5. 4  13  5 Look for products that are multiples of Use the Commutative Property. 13  4  5 13  (4  5) Use mental math to multiply. 13  20 Use the Associative Property to group compatible numbers.

Course Mental Math Check It Out: Example 1A Evaluate Look for sums that are multiples of Use the Commutative Property (12 + 8) + (5 + 5) Use mental math to add Use the Associative Property to make groups of compatible numbers.

Course Mental Math Check It Out: Example 1B Evaluate 8  3  5. 8  3  5 Look for products that are multiples of Use the Commutative Property. 3  8  5 3  (8  5) Use mental math to multiply. 3  40 Use the Associative Property to group compatible numbers.

Course Mental Math DISTRIBUTIVE PROPERTY WordsNumbers When you multiply a number times a sum, you can find the sum first and then multiply, or multiply by each number in the sum and then add. 6  (10 + 4) = 6  14 = 84 6  (10 + 4) = (6  10) + (6  4) = = 84

Course Mental Math When you multiply two numbers, you can “break apart” one of the numbers into a sum and then use the Distributive Property. Break the greater factor into a sum that contains a multiple of 10 and a one-digit number. You can add and multiply these numbers mentally. Helpful Hint

Course Mental Math Additional Example 2A: Using the Distributive Property to Multiply Use the Distributive Property to find the product. 6  35 6  35 = 6  (30 + 5) “Break apart” 35 into = 210 Use the Distributive Property. = (6  30) + (6  5) Use mental math to add. = Use mental math to multiply.

Course Mental Math Additional Example 2B: Using the Distributive Property to Multiply Use the Distributive Property to find the product. 9  87 9  87 = 9  (80 + 7) “Break apart” 87 into = 783 Use the Distributive Property. = (9  80) + (9  7) Use mental math to add. = Use mental math to multiply.

Course Mental Math Check It Out: Example 2A Use the Distributive Property to find the product. 4  27 4  27 = 4  (20 + 7) “Break apart” 27 into = 108 Use the Distributive Property. = (4  20) + (4  7) Use mental math to add. = Use mental math to multiply.

Course Mental Math Check It Out: Example 2B Use the Distributive Property to find the product. 6  43 6  43 = 6  (40 + 3) “Break apart” 43 into = 258 Use the Distributive Property. = (6  40) + (6  3) Use mental math to add. = Use mental math to multiply.

Course Mental Math Lesson Quiz Evaluate  5  Use the Distributive Property to find each product    