At a restaurant, 4 people ordered 3 pieces of cheesecake each. 🍰
How many pieces of cheesecake did they order in all?
You could use addition, but that would be slow. 😴
Let's use multiplication instead.
You learned a lot about multiplication in third grade. Don't worry if you forgot.
In this lesson, we'll review.
Multiplication is a shortcut for repeated addition.
To add these groups, we write:
3 + 3 + 3 + 3 = 12
To multiply instead, we write:
4 groups of 3 objects = 12
or
4 × 3 = 12
(4 times 3 equals 12)
Great work. You just wrote a multiplication equation.
× is the multiplication sign.
Every multiplication equation has three parts:
The factors are the numbers you multiply together.
Tip: Some people call them the multiplicand and multiplier, but 'factors' is more common.
The answer to a multiplication operation is called the product.
The product of multiplication stays the same even if we change the order of its factors.
This is called the commutative property of multiplication.
The factors can commute, or move around each other, and the answer stays the same.
For example, 5 × 3 and 3 × 5 are both equal to 15.
3 × 5 = 15
and
5 × 3 = 15
Let's use multiplication to quickly count the number of circles here:
How many equal groups do you see in this model?
Correct! 4 groups.
So, 4 is one of the factors.
4 × ____ = ?
How many circles are there in each group?
Very good! There are 2 circles in each group.
So, 2 is the other factor.
4 × 2 = ?
Now, we can quickly find the product:
4 × 2 = 8
Great job! 👏
How many equal groups are there?
There are 7 groups of 4 circles in this picture.
So, we can write this as:
7 × 4 = 28
or
4 × 7 = 28
Awesome!
You just reviewed the basics of multiplication. 🎉
Now, let's practice.