1. Subtraction of Whole Numbers
Unit 2
Subtraction of Whole Numbers

2. Basic Principles of Subtraction of Whole Numbers
Subtraction is the process of finding the difference, or remainder, between two numbers or quantities.
The number to be subtracted (subtrahend) is placed under the number from which it is to be subtracted (minuend) with both numbers aligned on the right side.

3. Basic Principles of Subtraction of Whole Numbers
Starting at the right side, subtract the bottom number from the top number.
If the number being subtracted is larger than the number it is to be subtracted from, borrow 1 number from the digit to the left and add 10 to the number that is too small.
Then subtract 1 from the digit used for borrowing before using it to subtract the number below it.

4. Subtraction of Whole Numbers
Example: Subtract 289 from 942
The number to be subtracted goes on the bottom:

5. Subtraction of Whole Numbers
Because 9 is greater than 2, borrowing is required.
Four can be written as 3 tens plus 1 ten.
Borrow 1 ten to increase the 2 to 12, leaving 3 tens.
Nine can now be subtracted from 12 for a difference of 3.

6. Subtraction of Whole Numbers
Now look at the second column. Eight is greater than 3, so borrowing is required again.
Nine can be written as 8 hundreds plus 1 hundred, or 10 tens.
Borrow 1 hundred to increase the 3 to 13, leaving 8 hundreds.
Eight can now be subtracted from 13 for a difference of 5.
Subtract the hundreds column.

7. Subtraction of Whole Numbers
An easy way to check your answer when subtracting whole numbers is to add the answer (difference) to the subtrahend (number subtracted).
If you get the minuend (original number), your answer is correct.

8. Practical Problem
A student in a health science statistics course is studying statistics on acquired immune deficiency syndrome (AIDS) from the Centers for Disease Control and Prevention (CDC). The statistics show a total of 816,149 patients with AIDS. Of this number, 467,910 patients have died.
How many patients are still alive?

9. Practical Problem Subtract 467,910 from 816,149:
There are 348,239 patients still alive.