The tens complement is the number needed to make a single digit add up to 10. This technique is a building block for use in other tricks.
10’s complement of 7?
= 3
Step 1
Subtract the number that you are finding the 10’s complement of from 10.
10 - 7 = 3
Step 2
The result of step 1 is the 10’s complement.
3 is the 10’s complement of 7.
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This technique can be used with any large number. Simply take the 10’s complement of each digit to find the 10’s complement of the entire number.
10’s complement of 6347?
= 4763
Step 1
Subtract each digit in the number from 10.
10 - 6 = 4
10 - 3 = 7
10 - 4 = 6
10 - 7 = 3
= 4763