The number line is the graphical representation of a straight line on which numbers from the smallest to the largest are written. The number line is a tool for solving simple math problems, and is very useful with small numbers: if the problem you have to solve includes numbers greater than 20 or fractions, using it becomes a little too complicated. It is easy and useful to use the number line for adding and subtracting small numbers or for problems that use negative numbers.
Steps
Method 1 of 6: Draw the Number Line
Step 1. Draw a long straight line on a piece of paper
This will be the base of the number line.
You can draw it with a pen or highlighter if you want to use it multiple times
Step 2. Draw clearly visible dashes on the line
This will make it look like a track.
You can do this in pen too, if you want to use the line for more trouble
Step 3. Starting from the left, start writing the numbers above the dashes
Start from scratch on the first dash on the left.
- On each dash, write the next number. For example, on the dash after the one marked with zero, write 1.
- You can also write the numbers in pen, to reuse the number line multiple times.
Step 4. Stop when you get to 20
Remember: math problems with numbers greater than 20 make this method too complex.
Now the number line shows the numbers 0 to 20, from left to right
Method 2 of 6: Doing Additions with the Number Line
Step 1. Look at the calculation you need to solve
Determine which are the first and second numbers of the calculation.
For example, in 5 + 3 the first number is 5, while the second is 3
Step 2. On the number line, locate the first number that makes up the addition
Put your finger on it.
- From here you will start counting.
- For example, if your calculation is 5 + 3, you will need to put your finger on the 5 on the number line.
Step 3. Move your finger right to the next dash and number
You have moved 1 space.
If you start at 5, when you get to 6 you have moved 1 space
Step 4. Move your finger as many spaces as indicated by the second number of the addition, then stop
This way you will be sure to find the result of the calculation.
- Do not move more spaces than indicated by the second number of the addition.
- For example, if the second number is 3, you will need to move 3 spaces.
Step 5. Look at what number your finger is on now
This is the solution to the problem.
For example, if the calculation had been 5 + 3, you would have moved 3 spaces to the right starting from 5 and your finger would be on 8 on the number line. 5 + 3 = 8
Step 6. Try again a second time to check if your answer is correct
This will help you make sure you are getting the right result.
If during the check you get a different result, try again to check again
Method 3 of 6: Doing the Subtractions with the Number Line
Step 1. Look at the subtraction you need to solve
Determine which are the first and second numbers of the calculation.
In the calculation 7 - 2, 7 is the first number, while 2 is the second
Step 2. On the number line, locate the first number that makes up the subtraction
Put your finger on it.
If the calculation were 7 - 2, you would start by placing your finger on the 7 on the number line
Step 3. Move your finger left to the next dash and number
You have moved 1 space.
For example: if you start at 7, when you get to 6 you have moved 1 space
Step 4. Move your finger as many spaces as indicated by the second number of the subtraction, then stop
This way you will be sure to find the result of the calculation.
If the second number of the subtraction is 2, you will have to move your finger 2 spaces to the left
Step 5. Look at what number your finger is on now
This is the solution to the problem.
For example, in the 7 - 2 calculation, you would have started from 7 on the number line and moved 2 spaces to the left, ending with your finger on 5. 7 - 2 = 5
Step 6. Try again a second time to check if your answer is correct
This will help you make sure you are getting the right result.
If you get a different result during the check, try again to figure out where you went wrong
Method 4 of 6: Draw the Number Line with Negative Numbers
Step 1. Draw a new number line
Start by drawing a long straight line on a piece of paper.
This will be the base of the number line
Step 2. Draw clearly visible dashes on the line
This will make it look like a track.
If you have to do calculations with negative numbers, you will need to do more dashes than necessary for normal addition / subtraction problems
Step 3. Start numbering the dashes
Put zero on the dash in the center of the number line.
Put 1 to the right of zero and -1 to its left, then -2 will go to the left of -1 and so on
Step 4. Look at the number line when you are done
The zero must be in the center.
Try to go up to 20 on the right and up to -20 on the left
Method 5 of 6: Doing Additions with Negative Numbers
Step 1. Look at the problem you need to solve
Determine which are the first and second numbers of the calculation.
For example, in 6 + (-2), 6 will be the first number, while -2 will be the second
Step 2. Put your finger on the number line, on the first number of the calculation
In 6 + (-2) you would start by placing your finger on the 6 on the number line
Step 3. Move your finger to the left, to the next dash and number
Adding a negative number is like doing a normal subtraction. You have moved 1 space.
Step 4. Move your finger as many spaces as indicated by the second number, then stop
This way you will be sure to find the result of the calculation.
For example, if the second number in the calculation is -2, you will need to move your finger 2 spaces to the left
Step 5. Look at what number your finger is on now
This is the solution to the problem.
For example, in the calculation 6 + (-2), you would have started with your finger on 6 and you would have moved 2 spaces to the left, ending with your finger on 4. 6 + (-2) = 4
Step 6. Try again a second time to check if your answer is correct
This will help you make sure you are getting the right result.
If you get a different result during the check, try again to figure out where you went wrong
Method 6 of 6: Doing Subtractions with Negative Numbers
Step 1. Use the number line with negative numbers
You will need numbers greater than and less than zero.
Remember, in this number line the zero is in the center. All negative numbers will be to the left of zero, while all positive numbers will be to the right of zero
Step 2. Look at the subtraction you need to solve
Determine which are the first and second numbers of the calculation.
For example, in (-8) - (-3), the first number is -8, while the second is -3
Step 3. Put your finger on the first number of the calculation
You will start from here.
If the calculation were (-8) - (-3), you would start by placing your finger on -8 on the number line
Step 4. Move your finger right to the next dash and number
Subtracting a negative number is like doing a normal addition.
If you started at -8, you should now be at -7. You have moved 1 space
Step 5. Move your finger as many spaces as indicated by the second number, then stop
This way you will be sure to find the result of the calculation.
For example, if the second number in the calculation is -3, you should move 3 spaces on the number line
Step 6. Look at what number your finger is on now
This is the result of the subtraction.
For example, in the calculation (-8) - (-3), you started with your finger on -8 and moved 3 spaces to the right, arriving at -5. (-8) - (-3) = -5
Step 7. Try again a second time to check if your answer is correct
This will help you make sure you are getting the right result.
If you get a different result during the check, try again to figure out where you went wrong
Advice
- Use this method with small numbers.
- Using it for larger numbers would take a long time and it would be easy to make mistakes.
- Also, it is easier to use the number line for problems that contain integers. Avoid decimals and fractions.
