How to Add and Subtract Integers
Understand what a number line is., Draw a basic number line., Draw two marks, one on each side of your zero., Complete your number line by adding more numbers., Understand positive and negative integers., Start solving 1+2 by putting your finger on...
Step-by-Step Guide
-
Step 1: Understand what a number line is.
Number lines turn basic math into something real and physical that you can see in front of you.
By just using a few marks and some common sense, we can use them like calculators to add and subtract numbers. -
Step 2: Draw a basic number line.
Imagine or draw a straight, flat line.
Make a mark near the middle of your line.
Write a 0 or zero next to this mark.
Your math book might call this point the origin, since it's where numbers originate, or start from. , Write
-1 next to the mark on the left and 1 next to the mark on the right.
These are the integers closest to zero.
Don't worry about making the spacing perfect
- as long as you're close enough that you can tell what it's supposed to mean, the number line will work.
The left side is the side at the beginning of a sentence. , Make more marks to the left of
-1 and to the right of
1.
Moving left from
-1, label the next marks
-2,
-3, and
-4.
Moving right from 1, label the next marks 2, 3, and
4.
You can keep going if you have space on your paper.
The example image shows a number line from
-6 to
6. , A positive integer, also called a natural number, is an integer larger than zero. 1, 2, 3, 25, 99, and 2007 are all positive integers.
A negative integer is an integer less than zero (like
-2,
-4 and
-88).
An integer is just another way of saying a "whole number".
Fractions like 1/2 (one half) are only part of a number, so they are not integers.
Same with a decimal like
0.25 (zero point two five); decimals are not integers. , We're going to solve the simple addition problem 1+2 using the number line you just made.
The first number in this problem is 1, so start by putting your finger on that number.
Do you think this is too easy? If you've done any addition at all, you probably know the answer to 1+2.
That's good: if you know the answer it will be easier to understand how number lines work.
Then you can use a number line for more difficult addition problems, or to prepare you for more difficult math like algebra. , Slide your finger to the right, counting the number of marks (other numbers) you pass by.
Once you've hit 2 new marks, stop.
The number your finger is pointing to, 3, is the answer. , Suppose we're figuring out what 3 + 2 is.
Start at 3, move to the right or increase by
2.
We end up at
5.
This is written as 3 + 2 =
5. , For example, if we have 6
- 4, we start at 6, move left four spaces, and end up at
2.
This is written as 6
- 4 =
2. -
Step 3: Draw two marks
-
Step 4: one on each side of your zero.
-
Step 5: Complete your number line by adding more numbers.
-
Step 6: Understand positive and negative integers.
-
Step 7: Start solving 1+2 by putting your finger on the mark labeled 1.
-
Step 8: Add 1+2 by moving your finger 2 marks to the right.
-
Step 9: Add any positive integers by moving right on a number line.
-
Step 10: Subtract positive integers by moving left on a number line.
Detailed Guide
Number lines turn basic math into something real and physical that you can see in front of you.
By just using a few marks and some common sense, we can use them like calculators to add and subtract numbers.
Imagine or draw a straight, flat line.
Make a mark near the middle of your line.
Write a 0 or zero next to this mark.
Your math book might call this point the origin, since it's where numbers originate, or start from. , Write
-1 next to the mark on the left and 1 next to the mark on the right.
These are the integers closest to zero.
Don't worry about making the spacing perfect
- as long as you're close enough that you can tell what it's supposed to mean, the number line will work.
The left side is the side at the beginning of a sentence. , Make more marks to the left of
-1 and to the right of
1.
Moving left from
-1, label the next marks
-2,
-3, and
-4.
Moving right from 1, label the next marks 2, 3, and
4.
You can keep going if you have space on your paper.
The example image shows a number line from
-6 to
6. , A positive integer, also called a natural number, is an integer larger than zero. 1, 2, 3, 25, 99, and 2007 are all positive integers.
A negative integer is an integer less than zero (like
-2,
-4 and
-88).
An integer is just another way of saying a "whole number".
Fractions like 1/2 (one half) are only part of a number, so they are not integers.
Same with a decimal like
0.25 (zero point two five); decimals are not integers. , We're going to solve the simple addition problem 1+2 using the number line you just made.
The first number in this problem is 1, so start by putting your finger on that number.
Do you think this is too easy? If you've done any addition at all, you probably know the answer to 1+2.
That's good: if you know the answer it will be easier to understand how number lines work.
Then you can use a number line for more difficult addition problems, or to prepare you for more difficult math like algebra. , Slide your finger to the right, counting the number of marks (other numbers) you pass by.
Once you've hit 2 new marks, stop.
The number your finger is pointing to, 3, is the answer. , Suppose we're figuring out what 3 + 2 is.
Start at 3, move to the right or increase by
2.
We end up at
5.
This is written as 3 + 2 =
5. , For example, if we have 6
- 4, we start at 6, move left four spaces, and end up at
2.
This is written as 6
- 4 =
2.
About the Author
Deborah Ramos
Brings years of experience writing about lifestyle and related subjects.
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