2.1.9

Method I - Nines Complement Method

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Nines Complement Method: 753 − 491

Step 1

Step 1

  • Instead of subtracting from 753, we start by subtracting 491 from 999. It is easy to subtract any number from 999.
Step 2

Step 2

  • 508 is the ‘9s complement’ of 491.
  • Now add 508 to 753.
Step 3

Step 3

  • Subtract 1000 from the total, then add 1.
  • This is equivalent to subtracting 999.

Well done!

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1

Course Overview

1.1

Course Structure & Commonly Asked Questions

1.1.1Introduction to the Course & Common Questions
2

Subtraction Methods

2.1

Subtraction 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

Practice questions on Method I - Nines Complement Method

Can you answer these? Complete these activities in the Seneca app to progress towards your certificate.

  1. 1
    Which student has done the first step of the calculation 792,836 − 284,756 correctly?Multiple choice
  2. 2
    Which student has done the final step of the calculation 792,836 − 284,756 correctly? Multiple choice
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Method H - Complementary Method