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Saturday, December 14, 2013

Multiplication Basics

What is multiplication? 

Multiplication is when you take one number and add it together a number of times. 

Example: 

5 multiplied by 4 = 5 + 5 + 5 + 5 = 20 

We took the number 5 and added it together 4 times. This is why multiplication is sometimes called "times". 

More examples:
  • 7 x 3 = 7 + 7 + 7 = 21
  • 2 x 1 = 2
  • 3 x 6 = 3 + 3 + 3 + 3 + 3 + 3 = 18
Signs for Multiplication 

There are a few different signs that people use to indicate multiplication. The most common is the "x" sign, but sometimes people use a "*" sign or other symbols. Here are some ways to indicate 5 multiplied by 4.
  • 5 x 4
  • 5 * 4
  • 5 times 4
Sometimes when people use variables in multiplication they will just put the variables next to each other to indicate multiplication. Here are a few examples:
  • ab = a x b
  • (a +1)(b + 1) = (a +1) x (b + 1)
Factors and Products 

Sometimes when teachers talk about multiplication they will use the terms factors and products. 

Factors are the numbers you are multiplying together. Products are the answers. 

(factor) x (factor) = product 

Multiplying by Zero and One 

Zero and one are two special cases when multiplying. 

When multiplying by 0, the answer is always 0. 

Examples:
  • 1 x 0 = 0
  • 7676 x 0 = 0
  • 0 x 12 = 0
  • 0 x b = 0
When multiplying by 1, the answer is always the same as the number multiplied by 1. 

Examples:
  • 1 x 12 = 12
  • 7654 x 1 = 7654
  • 1 x 0 = 0
  • 1 x b = b
Order Doesn't Matter 

An important rule to remember with multiplication is that the order you multiply numbers doesn't matter. You can multiply them in any order you want and the answer will be the same. This can help sometimes when you get stuck on a problem. Just try it the other way. 

Examples:
  • 5 x 4 = 4 + 4 + 4 + 4 + 4 = 20
  • 4 x 5 = 5 + 5 + 5 + 5 = 20

  • 3 x 2 = 2 + 2 + 2 = 6
  • 2 x 3 = 3 + 3 = 6

  • 4 x 1 = 1 + 1 + 1 +1 = 4
  • 1 x 4 = 4 = 4
Multiplication Table 

Once you learn the basics of multiplication, you will want to learn the multiplication table, also called the times table. This table includes all of the possible multiplications between the numbers 1 to 12. That is all the way from 1 x 1 to 12 x 12. 

It may sound like a lot of useless work to memorize this table, but it will help you a LOT later in school. You will be able to solve harder problems faster and easier if you know these numbers by heart. 

Here is the table: 



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