We need to know a different ways to multiply...you might be asked to use a specific method to get your answer in a test like the PARCC. They are all related and all contain partial products.
The Expanded Algorithm 1
The Area Model
The Partial Product Method
Using the Distributive Property
Remember the Properties of Multiplication (you NEED to know these)
When two numbers are multiplied together, the product is the same regardless of the order of the multiplicands.
For example 4 x 2 = 2 x 4
When three or more numbers are multiplied, the product is the same regardless of the grouping of the factors.
For example (2 x 3) x 4 = 2 x (3 x4)
Multiplicative Identity Property:
The product of any number and one is that number.
For example 5 x 1 = 5.
The sum of two numbers times a third number is equal to the sum of each addend times the third number.
For example 4 x (6 + 3) = 4 x 6 + 4 x 3
Below are some fast multiplication tricks you can use in mental math...you might use these in a contest link the Math Olympiad.
Multiplication Tricks (you do NOT need to know this)