3.3 549 076 + 23 110 Estimate: 550 000 + 23 000 ≈ 573 000 550 000 − 549 076 = 924 23 000 − 23 110 = −110 924 + ( −110 ) = 814
549 076 + 23 110 = 573 000 − 814 = 572 186
3.5 556 984 − 443 056 Estimate: 560 000 − 440 000 ≈ 120 000 560 000 − 556 984 = 3 016 440 000 − 443 056 = −3 056 3 016 − ( −3 056 ) = 6 072 556 984 − 443 056 = 120 000 − 6 072 = 113 928
Remedial
• Since the basic multiplication facts are so important when doing long multiplication and long division as well as factorising whole numbers and estimation of answers, remediation of this must be done with those learners who have not mastered it yet.
• Some learners may have difficulty with long multiplication and long division. Let them attempt easy examples first and then progress to examples involving bigger whole numbers.
• Some learners may have difficulty with rounding off big whole numbers. Help them with this. They will probably also struggle with estimating the answer of some calculations and the skill of compensating. Let them attempt easy examples first and then progress to examples involving bigger whole numbers.
• Some learners may have difficulty with understanding the commutative, associative and distributive properties. Work through some more examples to help them with this.
Extension
• Challenge learners to investigate prime numbers beyond 100 and to find the biggest prime number they can determine.
• Encourage learners to do research on the history of the various notations of whole numbers: how the ancient Egyptians, the Babylonians and the Romans wrote whole numbers and how the Indians wrote whole numbers and were the first to use a symbol for 0.
3.6
3.4
998 432 − 654 008 Estimate: 1 000 000 − 650 000 ≈ 350 000 1 000 000 − 998 432 = 1 568 650 000 − 654 008 = −4 008 1 568 − (−4 008) = 5 576
998 432 − 654 008 = 350 000 − 5 576 = 344 424
198 008 − 88 999 Estimate: 200 000 − 90 000 ≈ 110 000 200 000 − 198 008 = 1 992 90 000 − 88 999 = 1 001 1 992 − 1 001 = 991
198 008 − 88 999 = 110 000 − 991 = 109 009
Chapter 1: Numbers and integers
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