Subtracting whole numbers
Subtracting whole numbers is the inverse operation of adding whole numbers. With subtraction, instead of adding two numbers to get a sum, you are removing one number from another to get a difference.
First, take a look at the simple subtraction problems above. These are subtractions with one digit and subtractions with one digit are usually fairly easy to do.
The first one is 8 − 4 = 4. Thinking about money, it is like you have 8 dollars and you spend 4, you are left with 4 dollars.
Things start getting complicated when you have more than one digit and you cannot remove the number at the bottom from the number on top such as when
doing 85 − 8.
Study the following example carefully because the concept of borrowing a ten is illustrated here.
Since you could not remove 8 from 5, you borrowed a ten from 8 tens and add that ten to 5 to make it 15.
You can also write the problem without the tens and the ones to make it look simpler as illustrated below.
Another example
Once again, study the following example carefully. If you understand it and the one before, you should be well on your way to mastering subtracting.
Step #1
You cannot remove 6 from 4. Therefore, borrow a 10 from 2 tens and then add that to 4 ones. The tens place now has 1 ten and the ones place now has 14 ones. The problem becomes:
Step #2
You cannot remove 5 from 1. Therefore, borrow 1 hundred from 4 hundreds and add that to 1 ten. 1 hundred = 10 tens. Add 10 tens to 1 ten to make it 11 tens. The hundreds place now has 3 hundreds.
Step #3
You cannot remove 7 from 3. Therefore, borrow 1 thousand from 5 thousands. 1 thousand = 10 hundreds.
Add 10 hundreds to 3 hundreds to make it 13 hundreds. The thousands place now has 4 thousands.
Finally, just subtract since all numbers at the bottom are now smaller than the number on top.
14 ones  6 ones = 8 ones
11 tens  5 tens = 6 tens
13 hundreds  7 hundreds = 6 hundreds
4 thousands  0 thousands = 4 thousands
Check how well you understood this lesson about subtracting whole numbers with the quiz below.

Jul 03, 20 09:51 AM
factoring trinomials (ax^2 + bx + c ) when a is equal to 1 is the goal of this lesson.
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