FOUR BASIC ARITHMETIC OPERATIONS
Review of Introductory Mathematics
Thus, the difference of 5 - 3 is not the same as 3 - 5. The associative law for addition permitted
combining addends in any order. In subtraction, this is not allowed.
(a-b)-c a-(b-c)
Example:
(10-5)-1 10-(5-1)
4 6
When subtracting two numbers, the subtrahend is placed under the minuend with the digits
arranged in columns placing the units place under the units place, the tens column next, and so
on.
Example:
Subtract 32 from 54.
Solution:
54
-32
22
Whenever the digit in the subtrahend is larger than the digit in the minuend in the same column,
one place value is borrowed from the next digit to the left in the minuend. Refer to the
following example.
Example:
Subtract 78 from 136.
Solution:
2
13/6
- 78
58
When subtracting the units column, 6 - 8, a 10 is borrowed from the tens column. This
now makes subtracting the units column 16 - 8. An 8 is placed under the units column.
Next the tens column is subtracted.
A 10 was borrowed from the tens column and now 7 is subtracted from 12, not 13. This
yields: 12 - 7 = 5. The 5 is placed under the tens column and the difference is 58.
This can be done for any subtraction formula. When the digit in the subtrahend column
is larger than the digit in the minuend in the same column, a number from the next higher
place position column is "borrowed." This reduces the higher position column by one.
MA-01
Page 10
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