Lesson Plan - Get It!
Ray works at a grocery store. At the end of the day, he has to take inventory of how much food he has in his store.
He could count each vegetable and fruit, but that would take forever!
Instead, Ray can use what he knows about multiplication to help him take inventory.
- There are 6 cases of bananas. Each case has 10 bananas.
- There are 4 cases of cucumbers. Each case has 20 cucumbers.
- There are 7 cases of apples. Each case has 50 apples.
- There are 4 cases of peppers. Each case has 80 peppers.
- There are 3 cases of oranges. Each case has 90 oranges.
- There are 4 cases of cherries. Each case has 200 cherries.
- How can you help Ray quickly figure out how many fruits and vegetables are left in the store?
First, look at the bananas.
There are 6 cases of bananas. Each case has 10 bananas.
You know this is multiplication because there are equal groups, and you are looking for a total.
You can solve this multiplication problem by drawing and counting the total bananas or by skip counting.
6 x 10 = 60
Ray has 60 bananas.
Now, look at the cucumbers:
There are 4 cases of cucumbers. Each case has 20 cucumbers.
This multiplication equation would look like this.
4 x 20 = ?
- What do you notice about this equation?
20 is a bigger number and not a factor you have learned in your multiplication facts.
20 is also a multiple of 10.
The multiples of 10 are 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 …
For a refresher on the multiples of 10, listen to the song in this fun video.
Since 20 is a multiple of 10, there is a shortcut to solving this multiplication equation!
First, 20 can be split into 2 x 10, so the equation can also be written like this.
Then, you can use the associative property to solve the problem easily.
Ray has 80 cucumbers!
Look at one more before you practice on your own.
There are 7 cases of apples. Each case has 50 apples.
This can be set up as the multiplication equation 7 x 50.
Follow the steps below to solve the problem.
- How can you tell if a number is a multiple of 10?
- How can you solve these types of problems using mental math?
- What would you do if you saw a problem like 6 x 300?
To learn other tricks to multiplying with multiples of 10, watch the following video.
Now, move to the Got It? section to practice and finish helping Ray at the grocery store.