Subjects
Grades
Subtraction
Concept sheet | Mathematics
Secondary
1-2
Subtraction is an operation that involves removing one quantity from another, finding a missing quantity, or comparing quantities. The numbers that make up the subtraction are called terms.
The difference is the result of this operation.
Words Signaling a Subtraction in a Word Problem
The following words are used to indicate a subtraction in a word problem.
|
Word |
Example |
Calculation |
|---|---|---|
|
Difference |
What is the difference between |8| and |4|? |
|8-4| |
|
Take away |
We take away |3| from |12.| |
|12-3| |
|
Decrease |
The number of students in the school decreased by |100.| |
|-100| |
|
Drop |
During the last |5| years, the sea level has dropped |2| m. |
|-2| |
|
Lose |
A company lost |$10\ 000|. |
|-10\ 000| |
|
Descend |
A person descended |15| floors of a building. |
|-15| |
The Concept of Regrouping
In a subtraction, transform a ten into 10 ones when the value of the digit above is smaller than the value of the digit to be subtracted.
Note: the same technique is used to regroup hundreds, thousands, etc.
Consider the following subtraction.
-
Subtract the ones
|
Since the value of the ones in the top number is smaller than the value of the ones in the bottom number, regroup a ten from the 5. Now, only 4 tens remain. This ten becomes 10 ones which are then added to the 2 existing ones. This gives 12 ones. |
 |
Subtract: 12 ones - 8 ones = 4 ones |
-
Subtract the tens
|
Since the value of the tens in the top number is smaller than the value of the tens in the bottom number, regroup 1 hundred from 3. Now only 2 hundreds remain. This hundred becomes 10 tens which are then added to the 4 existing tens. This gives 14 tens. |
 |
Subtract: 14 tens - 9 tens = 5 tens |
-
Subtract the hundreds
 |
Subtract: 2 hundreds - 0 hundreds = 2 hundreds |
The final answer is 2 hundreds, 5 tens, and 4 ones, which is 254.