Properties of Addition Commutative e.g. 4 + 2 = 2 + 4 We can picture this as follows: Show that the answers for each of these questions are the same 10 + 13 + 7 + 9 13 + 9 + 7 + 10 7 + 10 + 9 + 13 Which of these sums will not have the same answer as the rest? 12 + 20 + 42 + 18 20 + 12 + 18 + 42 42 + 20 + 18 + 20 18 + 12 + 20 + 42 Fill in the gaps to make these statements true : 22 + 11 + 9 + 3 = 11 + 9 + ___ + 22 = ___ + 11 + 3 + 22 14 + 4 + 2 + 16 = 16 + 4 + 14 + ___ = 4 + 2 + 16 + ___ Does the same work for subtraction? Try it and see if you can find things that work. Rearranging to make questions more manageable: You can use the associative property of addition to make questions much easier to handle. For example: 49 + 17 + 12 + 3 + 1 = (49 + 1) + (17 + 3) + 12 = 82. See if you can solve these easily by rearranging: 36 + 21 + 17 + 4 + 13 83 + 18 + 6 + 27 + 14 40 + 68 + 14 + 22 + 6 402 + 205 + 66 + 2 + 15 191 + 72 + 66 + 2 + 18 + 2 Summing Up! In this lesson, you’ll practice how to make addition and subtraction easier by breaking down numbers. It’s much easier to aim for ‘easy numbers’ such as the nearest ten, fifty, hundred, thousand etc rather than going straight for the ‘goal’.
Properties of Addition Commutative e.g. 4 + 2 = 2 + 4 We can picture this as follows: Show that the answers for each of these questions are the same 10 + 13 + 7 + 9 13 + 9 + 7 + 10 7 + 10 + 9 + 13 Which of these sums will not have the same answer as the rest? 12 + 20 + 42 + 18 20 + 12 + 18 + 42 42 + 20 + 18 + 20 18 + 12 + 20 + 42 Fill in the gaps to make these statements true : 22 + 11 + 9 + 3 = 11 + 9 + ___ + 22 = ___ + 11 + 3 + 22 14 + 4 + 2 + 16 = 16 + 4 + 14 + ___ = 4 + 2 + 16 + ___ Does the same work for subtraction? Try it and see if you can find things that work. Rearranging to make questions more manageable: You can use the associative property of addition to make questions much easier to handle. For example: 49 + 17 + 12 + 3 + 1 = (49 + 1) + (17 + 3) + 12 = 82. See if you can solve these easily by rearranging: 36 + 21 + 17 + 4 + 13 83 + 18 + 6 + 27 + 14 40 + 68 + 14 + 22 + 6 402 + 205 + 66 + 2 + 15 191 + 72 + 66 + 2 + 18 + 2 Summing Up! In this lesson, you’ll practice how to make addition and subtraction easier by breaking down numbers. It’s much easier to aim for ‘easy numbers’ such as the nearest ten, fifty, hundred, thousand etc rather than going straight for the ‘goal’.
properties-of-addition.docx