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&&66 8VHSDUHQWKHVHVEUDFNHWVRUEUDFHVLQQXPHULFDOH[SUHVVLRQV AF 1.2*2$ Use a letter to represent an unknown number; write and DQGHYDOXDWHH[SUHVVLRQVZLWKWKHVHV\PEROV evaluate simple algebraic expressions in one variable by substitution. UNDERLYING SKILLS AND CONCEPTS: add, subtract, multiply, and divide with whole numbers Use Properties for Mental Math You can use the properties of addition and multiplication to compute using mental math. Commutative Property of Addition: Changing the order of the addends does not change the sum. Commutative Property of Multiplication: Changing the order of the factors does not change the product. Distributive Property: Multiplying a sum by a number is the same as multiplying each addend by the number and then adding the products. E x am p l E 1 Use mental math to find the sum of 18 ! 7 ! 2. Use the commutative property of addition to write the addends in a different order. E – © CSL Associates, Inc. All rights reserved. 18 ! 7 ! 2 " 18 ! 2 ! 7 " 20 ! 7 " 27 E x am p l E 2 Use mental math to find the product of 4 # 35. Use the distributive property. 4 # 35 " (4 # 30) ! (4 # 5) " 120 ! 20 " 140 page 104 Chapter 9 – Lesson 4 Name P RAC T I C E Use mental math to find each sum. 1. 35 7 3 45 2. 8 15 12 35 3. 54 9 1 64 4. 4 52 4 60 5. 15 72 5 92 6. 18 36 2 56 8. 28 5 2 280 9. 12 4 10 480 2 94 188 Use mental math to find each product. E – © CSL Associates, Inc. All rights reserved. 7. 5 12 2 120 10. 3 42 126 11. 13. 21 7 147 14. 32 25 4 3,200 Math Reasoning 12. 17 5 85 15. 50 93 2 9,300 Use Properties for Mental Math MR 2.3 16. How does the commutative property help you find sums and products using mental math? I can change the order of the addends or factors so that I can do the easy computations first. Chapter 9 – Lesson 4 page 105 MCX94.HW.CL.G5.FM&Lesson.v211 8/2/04 18:02 Page 72 Name …at home! P RAC T I C E Use mental math to find each sum. 1. 67 4 3 74 2. 6 36 14 56 3. 75 9 1 85 4. 3 82 8 93 5. 15 43 5 63 6. 16 34 2 52 8. 38 5 2 380 9. 15 4 5 300 2 73 146 Use mental math to find each product. 150 10. 4 42 168 11. 13. 22 8 176 14. 21 25 4 2,100 Math Reasoning 12. 19 5 95 15. 50 2 68 6,800 Use Properties for Mental Math MR 2.3 16. How does the commutative property help you find sums and products using mental math? I can change the order of the addends or factors so that I can do the easy computations first. page 72 Home Resource and Homework Chapter 9 Lesson 4 E – © CSL Associates, Inc. All rights reserved. 7. 5 15 2 MCX94TEG5CH01_32.v7.4.2 2/24/01 19:44 Page 195 Name P RAC T I C E Use mental math to find each sum. 1. 35 7 3 45 2. 8 15 12 35 3. 54 9 1 64 4. 4 52 4 60 5. 15 72 5 92 6. 18 36 2 56 8. 28 5 2 280 9. 12 4 10 480 2 94 188 Use mental math to find each product. E – © CSL Associates, Inc. All rights reserved. 7. 5 12 2 120 10. 3 42 126 11. 13. 21 7 147 14. 32 25 4 3,200 Math Reasoning 12. 17 5 85 15. 50 93 2 9,300 Use Properties for Mental Math MR 2.3 16. How does the commutative property help you find sums and products using mental math? I can change the order of the addends or factors so that I can do the easy computations first. Chapter 9 – Lesson 4 Student Book Page page 105 Name …at home! P RAC T I C E Use mental math to find each sum. 1. 67 4 3 74 2. 6 36 14 56 3. 75 9 1 85 4. 3 82 8 93 5. 15 43 5 63 6. 16 34 2 52 8. 38 5 2 380 9. 15 4 5 300 2 73 146 Use mental math to find each product. 150 10. 4 42 168 11. 13. 22 8 176 14. 21 25 4 2,100 Math Reasoning 12. 19 5 95 15. 50 2 68 6,800 Use Properties for Mental Math MR 2.3 16. How does the commutative property help you find sums and products using mental math? I can change the order of the addends or factors so that I can do the easy computations first. page 72 Home Resource and Homework Chapter 9 Lesson 4 E – © CSL Associates, Inc. All rights reserved. 7. 5 15 2