Technique explanation
Teaching Explanation
A complement is the value that, when added to a number, completes it to the nearest round base such as 10, 100, or 1000. It is the distance from the number to the next power of ten. Complements support near-base calculation strategies by expressing numbers as offsets from stable anchors.
Method Conditions
Use when a number is near a power of 10 such as 10, 100, or 1000.
Standard Fallback
Use standard subtraction from the base, for example 100 − 73, with column borrowing.
Misconception and Correction
Misconception: The complement of 40 to 100 is 50.
Correction: The complement must reach exactly 100. Since 40 + 60 = 100, the complement is 60.
Module
Worked examples
Worked Examples
- Find the complement of 8 to the base 10. Calculation: 10 − 8 = 2. Verification: 8 + 2 = 10.
- Find the complement of 73 to the base 100. Calculation: 100 − 73 = 27. Verification: 73 + 27 = 100.
Academy Course
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