Review of Introductory Mathematics
FOUR BASIC ARITHMETIC OPERATIONS
When several numbers are added together, it is easier to arrange the numbers in columns with
the place positions lined up above each other. First, the units column is added. After the units
column is added, the number of tens is carried over and added to the numbers in the tens column.
Any hundreds number is then added to the hundreds column and so on.
Add 345, 25, 1458, and 6.
When adding the units column, 5 + 5 + 8 + 6 = 24. A 4 is placed under the units
column, and a 2 is added to the tens column.
Then, 2 + 4 + 2 + 5 = 13. A 3 is placed under the tens column and a 1 is carried over
to the hundreds column. The hundreds column is added as follows: 1 + 3 + 4 = 8.
An 8 is placed under the hundreds column with nothing to carry over to the thousands
column, so the thousands column is 1. The 1 is placed under the thousands column, and
the sum is 1834. To verify the sum, the numbers should be added in reverse order. In
the above example, the numbers should be added from the bottom to the top.
Subtracting Whole Numbers
When numbers are subtracted, the result is called the remainder or difference. The number
subtracted is called the subtrahend; the number from which the subtrahend is subtracted is called
the minuend. Subtraction is indicated by the minus sign (-).
Remainder or Difference
Unlike addition, the subtraction process is neither associative nor commutative. The commutative
law for addition permitted reversing the order of the addends without changing the sum. In
subtraction, the subtrahend and minuend cannot be reversed.
a - b =/ b - a