27
Week 9
Multiplication and Arrays
Multiplication and Arrays
We are going to look at the relationship between addition and multiplication!
We are also going to look at arrays.
When we multiply numbers we are adding a number repeatedly.
Multiplication
So here we have 2x4 which means we are going to add 2 four times!
So let’s do it!
2+2+2+2 = 8
So 2x4= 8
We can also look at this as 4 groups of 2.
Let's look at this another way!
4x2
If 2 X 4 = 8 then 4 x 2 = 8
Ok, let's examine this notion further!
Let's make 2 groups of 4:
xxxx xxxx
4 + 4 = 8
And now let's make 4 groups of 2:
xx xx xx xx
2 + 2 + 2 + 2 = 8
Multiplication Arrays
A multiplication array is simply an arrangement of rows or columns that matches a multiplication equation.
When describing multiplication we often say "groups" for example 3 groups of 6. But when we use arrays we can think of these groups as "rows or columns". I'm just going to use rows to avoid confusion.
Arrays
Here we have an array for 3 x 6 with 3 rows of 6.
We also have
6 x 3 with 6 rows of 3.
Both arrays should equal 18, but lets count the rows to make sure.
Making Arrays!
You can make arrays in many ways.
Here is an array for 2 x 4 and 4 x 2 made of stars!
2 rows of 4.
4 rows of 2
2x4 & 4x2
Here is an array for 4 x 8 made of fruit loops!