Multiply Multiples of 10

Contributor: Ashley Nail. Lesson ID: 13417

How well do you know your math facts? 2x7, 8x4, 3x9. What about the tens' table? 3x10, 7x10, 6x10. Use the multiples of 10 to solve even harder multiplication problems!

categories

Arithmetic, Rules and Properties

subject
Math
learning style
Auditory, Kinesthetic, Visual
personality style
Beaver
Grade Level
Intermediate (3-5)
Lesson Type
Quick Query

Lesson Plan - Get It!

Audio:

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!

fruits and vegetables

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 we help Ray quickly figure out how many fruits and vegetables are left in the store?

First, let's look at the bananas:

There are 6 cases of bananas. Each case has 10 bananas.

We know this is multiplication because there are equal groups, and we are looking for a total.

bananas

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 let's 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, watch 10 TIME TABLES "ROCK" from songsofhigherlrng:

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:

equation

Then, we can use the associative property to easily solve the problem:

equation

Ray has 80 cucumbers!

Let's 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 Multiplying Multiples of 10 | FAST & EASY - Mental Math | Math Help with Mr. J from Math with Mr. J:

Now, move on to the Got It? section to practice and to finish helping Ray at the grocery store.

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