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1-5. Mental Math. Course 1. Warm Up. Problem of the Day. Lesson Presentation. Warm Up Find each sum or product. 1. 17 + 15 2. 29 + 39 3. 8(24) 4. 7(12) 5. 3(91) 6. 6(15). 32. 68. 192. 84. 273. 90. Problem of the Day Determine the secret number from the following clues:

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

  2. Warm Up Find each sum or product. 1.17 + 15 2. 29 + 39 3. 8(24) 4. 7(12) 5. 3(91) 6. 6(15) 32 68 192 84 273 90

  3. 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

  4. Learn to use number properties to compute mentally.

  5. Vocabulary Commutative Property Associative Property Distributive Property

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

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

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

  9. Look for sums that are multiples of 10 Use the Commutative Property. Use mental math to add. Use the Associative Property to make groups of compatible numbers. Check It Out: Example 1A Evaluate 12 + 5 + 8 + 5. 12 + 5 + 8 + 5 12 + 8 + 5 + 5 (12+8) + (5+5) 20 + 10 30

  10. Look for products that are multiples of 10 Use the Commutative Property. Use mental math to multiply. Use the Associative Property to group compatible numbers. Check It Out: Example 1B Evaluate 8  3  5. 8  3  5 38 5 3  (85) 3  40 120

  11. 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. When you multiply two numbers, you can “break apart” one of the numbers into a sum and then use the Distributive Property.

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

  13. “Break apart” 87 into 80 + 7. Use the Distributive Property. Use mental math to add. Use mental math to multiply. Additional Example 2B: Using the Distributive Property to Multiply Use the Distributive Property to find the product. 9  87 9  87 = 9  (80 + 7) = (980) + (9 7) = 720 + 63 =783

  14. “Break apart” 27 into 20 + 7. Use the Distributive Property. Use mental math to add. Use mental math to multiply. Check It Out: Example 2A Use the Distributive Property to find the product. 4  27 4  27 = 4  (20 + 7) = (420) + (47) = 80 + 28 =108

  15. “Break apart” 43 into 40 + 3. Use the Distributive Property. Use mental math to add. Use mental math to multiply. Check It Out: Example 2B Use the Distributive Property to find the product. 6  43 6  43 = 6  (40 + 3) = (640) + (63) = 240 + 18 =258

  16. Lesson Quiz Evaluate. 1. 18 + 24 + 2 + 6 2. 10  5  3 3. 13 + 42 + 7 + 8 Use the Distributive Property to find each product. 4. 8  12 5. 6  15 6. 5  34 7. 3  71 50 150 70 90 96 170 213

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