2.1.8
Method H - Complementary Method
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Complementary Method: 753 − 491
Find the complement of the subtrahend and add it to the minuend. The complement is the number we add to the subtrahend to get it to the nearest power of 10.
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Step 1
- Here we find the complement of 491 (i.e. what we add to 491 to make 1000). We can instantly write down 509 using the method described for calculating complements.
- Now we add the complement of the subtrahend to the minuend.
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Step 2
- And finally, we subtract 1000 from the difference.
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Breaking down the maths
- Here, we have worked out 753 + (1000 − 491) − 1000.
- Simplifying, we get 753 + (1000 − 491) − 1000 = 753 − 491 as required.
1Course Overview
1.1Course Structure & Commonly Asked Questions
2Subtraction: KS2/3
2.1Subtraction Methods
2.1.1Method A - Decomposition Method2.1.2Method B - Equal Addition Method2.1.3Method C - Expanded Form Method2.1.4Method D - Partitioning Method2.1.5Method E - Counting-Up Method2.1.6Method F - Constant Difference Method2.1.7Method G - Partial Differences Method2.1.8Method H - Complementary Method2.1.9Method I - Nines Complement Method
3Expanding Double Brackets: KS3/4
Jump to other topics
1Course Overview
1.1Course Structure & Commonly Asked Questions
2Subtraction: KS2/3
2.1Subtraction Methods
2.1.1Method A - Decomposition Method2.1.2Method B - Equal Addition Method2.1.3Method C - Expanded Form Method2.1.4Method D - Partitioning Method2.1.5Method E - Counting-Up Method2.1.6Method F - Constant Difference Method2.1.7Method G - Partial Differences Method2.1.8Method H - Complementary Method2.1.9Method I - Nines Complement Method
3Expanding Double Brackets: KS3/4
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