How to Use a Number Line

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A number line is a line drawing where numbers are written from smallest to largest. A number line can be a tool to do simple math problems. This is most helpful for doing problems with small numbers. If your math problem involves numbers over 20 or fractions, it might get a bit too hard to use this tool. It is easiest to use a number line to help you add and subtract small numbers. You can also use it to do problems with negative numbers. [1]

Method 1
Method 1 of 6:

Setting Up a Number Line

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  1. This will be the base of your number line. [2]
    • You can draw this in pen or marker, if you want to use your number line over and over again.
  2. This will make it look like a train track.
    • You can also make these in pen so you can use the number line for more than one problem.
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  3. Start with zero above the first hashmark on the left. [3]
    • At each hashmark, write the next number up. For example, above the hash mark next to zero, write 1.
    • You can write these in pen as well, so you can re-use the number line over and over again.
  4. Remember, doing math problems with numbers over 20 will make this method too hard.
    • Now your number line should read from 0 to 20, going from left to right.
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Method 2
Method 2 of 6:

Adding Using a Number Line

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  1. Determine which number is first in the problem and which is second. [4]
    • For example, in 5 + 3, the first number is 5 and the second number is 3.
  2. Put your finger there.
    • This is where you will start counting.
    • For example if your math problem is 5 + 3, you should put your finger on 5 on your number line.
  3. You have now moved 1 space.
    • If you start at 5, when you reach 6, you have moved 1 space.
  4. This will make sure you end on the answer to your problem. [5]
    • Don't move more spaces than the second number in your addition problem.
    • For example, if the second number in your problem is 3, you will move 3 spaces.
  5. That is the answer to your math problem. [6]
    • For example, if your math problem was 5 + 3, you would have moved 3 spaces to the right of 5. Your finger would be on 8 on your number line. 5 + 3 = 8.
  6. This will help you make sure you have the right answer to your math problem.
    • If you come up with a different answer during your check, try again to double check.
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Method 3
Method 3 of 6:

Subtracting Using a Number Line

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  1. Find which number is the first number in the problem and which is second.
    • In the problem 7 - 2, 7 is the first number in the problem and 2 is the second number in the problem.
  2. Put your finger there.
    • If your math problem was 7 - 2, you would start by putting your finger on 7 on your number line.
  3. You have now moved 1 space.
    • For example: if you start at 7, when you reach 6, you've traveled 1 space.
  4. This will make sure you end on the answer to your problem. [7]
    • If the second number in your problem is 2, you should have moved your finger to the left two spaces.
  5. That is the answer to your subtraction problem.
    • For example, in the problem 7 - 2, you would have started your problem at 7 on your number line. You would have moved 2 positions to the left, ending with your finger on 5 on your number line. 7 - 2 = 5.
  6. This is to check your answer.
    • If you get a different result from your check, try again to see where you made a mistake.
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Method 4
Method 4 of 6:

Making a Number Line with Negative Numbers

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  1. Start by making a long horizontal line on a piece of paper.
    • This will be the base of your number line.
  2. This will make your line look like a train track.
    • You will need to make more hashmarks on the line than for a simple addition/subtraction problem if you are working with negative numbers.
  3. Put zero on the hashmark in the center of your line. [8]
    • Put 1 to the right of zero and -1 to the left of zero. -2 will go to the left of -1 and so on.
  4. Zero should be in the middle.
    • Try numbering up to 20 on the right and -20 on the left.
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Method 5
Method 5 of 6:

Adding With Negative Numbers

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  1. Find the first and second numbers in the problem.
    • For example, in 6 + (-2), 6 would be the first number and -2 would be the second.
  2. Put it on the first number in your problem.
    • In 6 + (-2) you would start by putting your finger on 6 on your number line.
  3. Adding a negative number is very similar to regular subtraction. You have now moved 1 space. [9]
  4. This will make sure you end on the answer to your problem. [10]
    • For example, if the second number in your problem is -2, you should have moved your finger to the left 2 spaces.
  5. This is the answer to your addition problem. [11]
    • For example, if your problem was 6 + (-2), you would have started with your finger on 6. You would have moved your finger to the left two spaces, ending on 4. 6 + (-2) = 4.
  6. This is to check your answer.
    • If you get an answer when you check your problem, try again to see where you made your mistake.
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Method 6
Method 6 of 6:

Subtracting with Negative Numbers

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  1. You will need numbers less than zero and more than zero.
    • Remember, on your negative number line zero will be in the middle. All the negative numbers will be to the left of zero and all the positive numbers will be to the right of zero.
  2. Find what number is first and which is second in the problem. [12]
    • For example, in (-8) - (-3), the first number is -8 and the second is -3.
  3. This is where you will start.
    • If your problem was (-8) - (-3), you would put your finger on -8 on your number line.
  4. Subtracting a negative number is much like addition with regular numbers.
    • If you started on -8, you should now be on -7. You will have moved one space.
  5. This will make sure you end on the answer of your problem.
    • For example, if the second number in the problem is -3, you should have only moved 3 spaces on your number line.
  6. That number is the answer to your subtraction problem.
    • For example, in the problem (-8) - (-3), you would have started with your finger on -8 and would have moved 3 spaces to the right, ending on -5. (-8) - (-3) = -5.
  7. This is to check your answer.
    • If you don't get the same answer this time, try again to see where you made a mistake.
    • In a test, they always give you something for a reason. When they ask you something, it's for a specific chapter test.
    • Think why some information is there and which specific section it is associated with.
    • For example, you may be given a word problem about the line of sight, and the chapter may be on trigonometry.
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  • Question
    Using the number lines. 209-159, what do I do?
    Donagan
    Top Answerer
    Start at +209, then move 159 to the left.
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    Not Helpful 14 Helpful 10
  • Question
    How do I plot 6 - (-2) on a number line?
    Donagan
    Top Answerer
    Start at +6, then move 2 to the right.
    Thanks! We're glad this was helpful.
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    Not Helpful 15 Helpful 7
  • Question
    How do I divide on a number line?
    Donagan
    Top Answerer
    Here's a very simple example of how to do that: Let's say we're dividing 2 into 6. Begin with the section of the number line from zero to 6. Count two units from zero to 2. Count another two units from 2 to 4. Count another two units from 4 to 6. So we have found that a length of two units exactly fits inside the length of six units three times. Thus, 2 divides into 6 three times.
    Thanks! We're glad this was helpful.
    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
    Yes No
    Not Helpful 7 Helpful 6
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      References

      1. ↑ https://www.splashmath.com/math-vocabulary/number-sense/number-line
      2. ↑ https://www.cuemath.com/numbers/number-line/
      3. ↑ https://www.mathsisfun.com/number-line.html
      4. ↑ https://www.khanacademy.org/math/arithmetic/arith-review-add-subtract/arith-review-strategies-for-adding-within-100/v/correct-number-lines-for-addition-and-subtraction
      5. ↑ https://www.khanacademy.org/math/cc-third-grade-math/imp-addition-and-subtraction/imp-strategies-for-adding-two-and-three-digit-numbers/v/exercise-for-numberline-addition-and-subtraction
      6. ↑ https://www.khanacademy.org/math/arithmetic/arith-review-add-subtract/arith-review-strategies-for-adding-within-100/v/correct-number-lines-for-addition-and-subtraction
      7. ↑ https://www.khanacademy.org/math/cc-third-grade-math/imp-addition-and-subtraction/imp-strategies-for-adding-two-and-three-digit-numbers/v/exercise-for-numberline-addition-and-subtraction
      8. ↑ https://www.splashmath.com/math-vocabulary/number-sense/number-line
      9. ↑ https://www.splashmath.com/math-vocabulary/number-sense/number-line
      1. ↑ https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-negative-numbers-add-and-subtract/cc-7th-add-sub-neg-number-line/v/adding-negative-numbers-on-number-line-examples
      2. ↑ https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-negative-numbers-add-and-subtract/cc-7th-add-sub-neg-number-line/v/adding-negative-numbers-on-number-line-examples
      3. ↑ https://www.khanacademy.org/math/cc-seventh-grade-math/cc-7th-negative-numbers-add-and-subtract/cc-7th-sub-neg-intro/a/subtracting-negative-numbers-review

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