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What is Subtraction?If addition is the act of putting things together, subtraction is about taking things away. It could be as simple as eating two (2) apples from a pile of six (6) apples. You would wind up with four (4) apples left over. It could also be as complex as figuring out the number of organisms that die each year in a specific ecosystem.
Terms that tell you subtraction is happening:
Take some away.
Subtract an amount.
This minus that.
Give up some.
Setting up the ProblemsThe big symbol you will learn in subtraction is the minus sign. It's a little dash (-) that goes between the two numbers in the problem. The order of the numbers in subtraction is very important. In addition, you could move the numbers around and get the same answer. If you move numbers around in a subtraction problem, the answer will be wrong.
3 + 9 = 12
9 + 3 = 12
9 - 3 = 6
3 - 9 = -6 (See how the answer is in negative numbers? Totally wrong.)
The numbers in a subtraction problem also have special names. You don't need to memorize them, just know they have special names. The first value is the minuend. The second value (the one you are subtracting) is called the subtrahend. The answer in a subtraction problem is called the difference. Actually, you probably should remember that the answer in a subtraction problem is called the difference. You already know about sums (answers in addition problems).
Problem: 9 - 3 = 6
Subtracting Single-DigitsWe'll start easy and have you work with single-digit numbers that are less than 10. Since you are just starting out, you can do these problems with your fingers if you get stuck. The idea is simple. You start with a specific number of objects and you take a few away. If you start with four balls (4) and take away two balls (2) how many are left? 4 - 2 leaves you with two (2) balls left. Here are some examples.
1 - 1 = 0
2 - 1 = 1
2 - 2 = 0
5 - 1 = 4
5 - 2 = 3
5 - 3 = 2
5 - 4 = 1
5 - 5 = 0
9 - 1 = 8
9 - 2 = 7
9 - 3 = 6
9 - 4 = 5
9 - 5 = 4
9 - 6 = 3
9 - 7 = 2
9 - 8 = 1
9 - 9 = 0
Less Than Zero?While you can't have less than zero objects, there are numbers in math that are less than zero. These numbers are called negative numbers. They aren't angry, they are called negative because the numbers you usually use are called positive numbers. As you learn more subtraction you might start to see negative numbers. They have a dash in front of the number. Our earlier example showed you one (-6). You'll learn more later.
4 (Positive number greater than zero)
8 (Positive number greater than zero)
-2 (Negative number less than zero)
-7 (negative number less than zero)
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