1 5 Mental Math Warm Up Problem of

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

1 -5 Mental Math Warm Up Find each sum or product. 1. 2. 3. 4. 5. 6. Course 1 17 + 15 32 29 + 39 68 8(24) 192 7(12) 84 3(91) 273 6(15) 90

1 -5 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 1

1 -5 Mental Math Learn to use number properties to compute mentally. Course 1

1 -5 Mental Insert Lesson Math Title Here Vocabulary Commutative Property Associative Property Distributive Property Course 1

1 -5 Mental Math Mental math means “doing math in your head. ” Course 1

1 -5 Mental Math COMMUTATIVE PROPERTY (Ordering) Words You can add or multiply numbers in any order. Course 1 Numbers 18 + 9 = 9 + 18 15 2 = 2 15

1 -5 Mental Math ASSOCIATIVE PROPERTY (Grouping) Words Numbers When you are only adding or only (17 + 2) + 9 = 17 + (2 + multiplying, you 9) can group any of (12 2) 4 = 12 (2 4) the numbers together. Course 1

1 -5 Mental Math Additional Example 1 A: Using Properties to Add and Multiply Whole Numbers A. Evaluate 17 + 5 + 3 + 15 Look for sums that are multiples of 10 17 + 3 + 5 + 15 Use the Commutative Property. Use the Associative (17 + 3) + (5 + 15) Property to make groups of compatible numbers. 20 + 20 40 Course 1 Use mental math to add.

1 -5 Mental Math Additional Example 1 B: Using Properties to Add and Multiply Whole Numbers B. Evaluate 4 13 5 Look for products that are multiples of 10 13 4 5 Use the Commutative Property. 13 (4 5) Use the Associative Property to group compatible numbers. 13 20 Use mental math to multiply. 260 Course 1

1 -5 Mental Math Try This: Example 1 A A. Evaluate 12 + 5 + 8 + 5 Look for sums that are multiples of 10 12 + 8 + 5 Use the Commutative Property. (12 + 8) + (5 + 5) Use the Associative Property to make groups of compatible numbers. 20 + 10 30 Course 1 Use mental math to add.

1 -5 Mental Math Try This: Example 1 B B. Evaluate 8 3 5. 8 3 5 Look for products that are multiples of 10 3 8 5 Use the Commutative Property. 3 (8 5) Use the Associative Property to group compatible numbers. 3 40 Use mental math to multiply. 120 Course 1

1 -5 Mental Math DISTRIBUTIVE PROPERTY Words Numbers When you multiply a number times a sum, 6 (10 + 4) = 6 14 you can = 84 • find the sum first 6 (10 + 4) = (6 10) + (6 4) and then multiply, or = 60 + 24 • multiply by each = 84 number in the sum and then add. Course 1

1 -5 Mental Math When you multiply two numbers, you can “break apart” one of the numbers into a sum and then use the Distributive Property. Helpful Hint 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. Course 1

1 -5 Mental Math Additional Example 2 A: Using the Distributive Property to Multiply Use the Distributive Property to find the product. A. Evaluate 6 35 = 6 (30 + 5) “Break apart” 35 into 30 + 5. = (6 30) + (6 5) Use the Distributive Property. = Use mental math to multiply. = Course 1 180 + 210 30 Use mental math to add.

1 -5 Mental Math Additional Example 2 B: Using the Distributive Property to Multiply Use the Distributive Property to find the product. B. Evaluate 9 x 87. 9 87 = 9 (80 + 7) “Break apart” 87 into 80 + 7. = (9 80) + (9 7) Use the Distributive Property. = Use mental math to multiply. = Course 1 720 + 783 63 Use mental math to add.

1 -5 Mental Math Try This: Example 2 A Use the Distributive Property to find the product. A. Evaluate 4 x 27. 4 27 = 4 (20 + 7) “Break apart” 27 into 20 + 7. = (4 20) + (4 7) Use the Distributive Property. = Use mental math to multiply. = Course 1 80 + 108 28 Use mental math to add.

1 -5 Mental Math Try This: Example 2 B Use the Distributive Property to find the product. B. Evaluate 6 43 = 6 (40 + 3) “Break apart” 43 into 40 + 3. = (6 40) + (6 3) Use the Distributive Property. = Use mental math to multiply. = Course 1 240 + 258 18 Use mental math to add.

1 -5 Mental Insert Lesson Math Title Here Lesson Quiz Evaluate. 1. 18 + 24 + 2 + 6 50 2. 10 5 3 150 3. 13 + 42 + 7 + 8 70 Use the Distributive Property to find each product. 4. 8 12 96 5. 6 15 90 6. Angie wants to buy 3 new video games. How much will she need to save if each game costs $27? $81 Course 1