Objective: Students will build simple arrays and equal groups to build a conceptual understanding of multiplication.
Vocabulary: multiplication, array, equal group
Warm up Questions:
- How are addition and multiplication alike?
- How are addition and multiplication different?
Multiplication is adding groups that are the same size.
There are 3 groups of 2 candies.
You can add: 2 + 2 + 2 = 6
You can multiply 3 groups of 2 : 3 x 2 = 6
You can add 2 + 1 cupcakes.
You cannot multiply a group of 2 and a group of 1.
Why can’t you multiply a group of 2 and a group of 1?
Multiplication is a faster way to add equal groups.
The groups must be equal!
2 x 1 can mean..
Multiplication can also be shown with an array.
These are both arrays.
What do the arrays represent? Select all that apply
This array has 4 rows. There are 2 squares in each row.
We can find the total by adding 2 + 2 + 2 + 2 = 8.
Since the groups are all the same size, we can also multiply 4 groups of 2.
It looks like this: 4 x 2 = 8.
Math Error Analysis
What’s the mistake?
These groups are not equal! They can be added but not multiplied.
2 + 5 = 7
2 x 5 does equal 10 but it does not match the model.
- Would it be faster to add 6 seven times or multiply 6 x 7 once?