Subtraction
Basics on the topic Subtraction
Subtraction – Definition
The subtraction meaning is very simple. Subtract means to take away from a group. The next section will show an example of subtraction. There are many subtraction strategies but today the subtraction method we will look at is crossing out.
Solving Subtraction Problems
Sometimes we are faced with subtraction word problems, how do we solve these? For example, there were 14 leaves on the tree and the dinosaur ate 6 leaves, how many leaves are left? First, write a number sentence. A number sentence is a mathematical sentence made up of numbers and signs. When we write a number sentence for a subtraction problem, we use a subtraction symbol.
The number sentence is fourteen minus six equals something. After we write the number sentence, we can draw pictures of HOW MANY we are starting with to help us subtract.
Now that we've drawn the circles, let's subtract by crossing SIX off. How many circles are left?
Eight! Which means fourteen minus six is eight. Now that we’ve solved a simple subtraction problem, let’s review!
Subtraction – Summary
When we want to find out how many are left, we can use subtraction. These are the steps to keep in mind when subtracting.
Step #  What to do 

1  Write a number sentence. 
2  Draw pictures of how many we are starting with to help us subtract. 
3  Subtract by crossing off. 
4  Count how many are left. 
First, write a number sentence. Next, draw pictures of how many we are starting with to help us subtract. Then, subtract by crossing off. Finally, count how many are left. Still wondering how to work out subtraction? On this website you can find subtraction worksheets featuring subtraction questions as well as other activities including subtraction pictures and interactive exercises focussing on subtraction to 20 for KS1.
Transcript Subtraction
Mr. Squeaks and Imani are in the Land of the Dinosaurs and are observing them from a safe distance using binoculars. They spot a brontosaurus eating some leaves from a tree. Hmm, how many leaves did it eat? Let's help Mr. Squeaks and Imani calculate by "Subtracting Numbers up to Twenty". "Subtract means to take away from a group." If we want to help Mr. Squeaks and Imani find out how many leaves are left, we can use subtraction. The tree branch has fourteen leaves on it, and the brontosaurus ate six of the leaves. How do we subtract? First, write a number sentence. A number sentence is a mathematical sentence made up of numbers and signs. The number sentence we write is fourteen minus six equals. After we write the number sentence, we can draw pictures of HOW MANY we are starting with to help us subtract.
Drawing circles is simple, so for this example we will draw fourteen circles. Let's count together! one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen! Now that we've drawn the circles, let's subtract by crossing SIX off. One, two, three, four, five, six. How many circles are left? Let's count together! One, two, three, four, five, six, seven, eight! Fourteen minus six is eight, which means there are eight leaves left on the branch. Now they've spotted EIGHTEEN pterodactyls and eight of them just flew away! How many pterodactlys are left? Remember, to help them subtract, we first write the number sentence. What is the number sentence? The number sentence is eighteen minus eight equals because there were EIGHTEEN pterodactyls and EIGHT flew away. What is the next step? The next step is to draw eighteen circles. What do we do now? Now we need to subtract eight from eighteen, by crossing off eight circles. How many circles are left? Let's count together! One, two, three, four, five, six, seven, eight, nine, ten! Eighteen minus eight is ten, which means there are ten pterodactyls left. Before we see what they spot next, let's remember. When we want to find out how many are left, we can subtract. First, write a number sentence. Next, draw pictures of HOW MANY we are starting with to help us subtract. Then, subtract by crossing off. Finally, count how many are left. Let's see what Mr. Squeaks and Imani are up to now. "Oh no, did you hear that!?"
"My turn!"
Subtraction exercise

How can we solve a subtraction problem?
HintsWhen you subtract, you are taking away from a group.
Once you cross off the circles you are subtracting, the remaining circles are your difference, or in other words, the answer.
SolutionThe steps for subtracting with word problems are:
 Write a number sentence.
 Draw circles to show the starting number.
 Cross off circles to subtract, or take away.
 Count how many circles are left. This is the difference.

Which picture helps us to solve each subtraction number sentence?
HintsThe first number in the number sentence should match the total number of circles.
Look at the example. There are five circles in the group altogether. The number sentence is telling you to subtract, or take away, two circles. Use this picture to help you complete the task.
The number you are subtracting should match how many circles are crossed off.
Solution When you create a drawing to match a number sentence, first draw the total number of circles at the beginning of the sentence. For example, in the problem 15  4 = 11, begin by drawing 15 circles to represent the starting number.
 Then, subtract by crossing off the number of circles you are taking away. For example, in the problem 15  4 = 11, you need to take away, or subtract 4. So, you should cross off 4 circles.
 Finally, the remaining circles will be your difference, or answer! For example, in the problem 15  4 = 11, there will be 11 circles remaining, which is your answer.

How many eggs are still to hatch?
HintsHow many dinosaur eggs are there altogether? This should be the beginning number in your subtraction sentence.
Take away the number of dinosaur eggs that have hatched. How many remain?
Remember the definition of what it means to subtract.
SolutionTo begin, find the total number of dinosaur eggs: 11. This will be the first number in your number sentence.
11
Next, work out how many dinosaur eggs you need to take away. We are looking for only the dinosaur eggs that remain unhatched, so that means we need to take away the 9 hatched eggs.
11  9 = ?
Finally, count the remaining unhatched eggs to find the difference: 2.
11  9 = 2

Solve the subtraction problems.
HintsThe difference or the answer to these subtraction problems is how many circles are left over. Count the remaining red circles to solve each problem.
To solve 14  7, we can draw 14 circles and cross 7 off. There are 7 red circles left, so the answer is 7.
SolutionWhen you subtract, you take away from a group. The remaining number is your difference, or answer.
 10  5 = 5
 6  4 = 2
 13  7 = 6
 9  1 = 8

What is 8  3?
HintsTo solve 8  3, we start with 8 circles and cross 3 off. Highlight the remaining circles that have not been crossed off to find the difference.
Count how many circles you highlighted and highlight that number at the bottom.
SolutionIn the subtraction sentence, 8  3 = ?, you begin with 8 circles and must take away 3 to find the remaining difference. You should highlight the 5 remaining circles. This is the answer.

Can you help Mr. Squeaks and Imani?
HintsDraw circles to help you find the answers.
Start with the total number of circles at the beginning of the number sentence. Then, cross out the amount you are subtracting. Count the left over circles to find your answer.
Each answer should have three number sentences that match!
Solution5
 11  6 = 5
 17  12 = 5
 9  4 = 5
 12  6 = 6
 6  0 = 6
 14  8 = 6
 9  2 = 7
 13  6 = 7
 15  8 = 7