Multiplying by multiples of 10

Multiplying by 10 and 100:
Count by each number 5 times.
5 x 1 = 5 5 x 1,000 = 5,000
5 x 10 = 50 5 x 10,000 = 50,000
5 x 100 = 500
Remember to think of it as
5 groups of ____

What will we learn today?
• Today, instead of counting by equal groups, we will use two strategies to help us multiply.
• 1: We will use the associate property to make multiplying easier.
• 2: We will use place value to make multiplying easier.

Let’s look at this one:
5 x 4 0
Think back to the associative property from yesterday….

Let’s look at this one:
40
5 x 4 0 = 5 x (4 x 10)

Let’s look at this one:
20
5 x 4 0 = (5 x 4) x 10

Let’s look at this one:
5 x 4 0 = x 10 = 200
5 x 40 = 200

EngageNY
12
120
60
9
90
15
150

Use what we just learned to solve this with your group….
20 x 4 = 2 x 10 x 4

Use what we just learned to solve this with your group….
20 x 4 = 2 x 4 x 10

Use what we just learned to solve this with your group….
8
20 x 4 = (2 x 4) x 10

Use what we just learned to solve this with your group….
20 x 4 = 8 x 10

Use what we just learned to solve this with your group….
20 x 4 = 8 x 10
8 x 10 = 10 x 8

Let’s look at this one again:
20
5 x 4 0
With one zero, it’s like multiplying by a 10, or moving the number over one place value from
20 ones to 20 tens.
20 tens = 200!

Let’s look at this one again:
20 tens
5 x 40 = 5 x 4 tens
With one zero, it’s like multiplying by a 10, or moving the number over one place value from
20 ones to 20 tens.
20 tens = 200!

Here’s another example…
12
12
12
120

15
15
8
8
15
150
8
80
EngageNY

Use what we just learned to solve this with your group….
20 x 4 = 2 tens x 4
= 8 tens
= 80
3 x 80 = 3 x 8 tens = 24 tens = 240

Let’s look at multiplying by multiples of 10 again.

By the end of this lesson, you will be able to answer this problem!
50 x 400

5 x 1 = 5 5 x 1,000 = 5,000
5 x 10 = 50 5 x 10,000 = 50,000
5 x 100 = 500

Let’s look at this one yet again…
20
5 x 4 0
200

Here’s what you should know….
• You can use the associative property:
5 x 60 = 5 x (6 x 10)

Here’s what you should know….
• You can use the associative property:
5 x 60 = (5 x 6) x 10

Here’s what you should know….
• You can use the associative property:
5 x 60 = (5 x 6) x 10 = 30 x 10

Here’s what you should know….
• You can use the associative property:
5 x 60 = (5 x 6) x 10 = 30 x 10 = 300
• When you multiply by 10, you move it to the left one place value.

Here’s what you should know….
• You can use the associative property:
5 x 60 = (5 x 6) x 10 = 30 x 10 = 300
• When you multiply by 10, you move it to the left one place value. When you multiply by 100, you move it over 2 place values.
30 x 100 = 3,000

Here’s what you should know….
• You can use the associative property:
5 x 60 = (5 x 6) x 10 = 30 x 10 = 300
• When you multiply by 10, you move it to the left one place value. When you multiply by 100, you move it over 2 place values.
30 x 100 = 3,000
• What do you think happens when you multiply by 1,000? 10,000?
30 x 1,000 = 30,000
30 x 10,000 = 300,000

Here’s what you should know….
• You can use the associative property:
5 x 60 = (5 x 6) x 10 = 30 x 10 = 300
• When you multiply by 10, you move it to the left one place value. When you multiply by 100, you move it over 2 place values.
• If you know this, you can take the shortcut!
• 1: Find your basic fact and multiply.
• 2: Count the number of zeros in the factors.
• 3: Add the same number of zeros to the product!

Multiplying by 10 and 100
50 x 3 = 150 5 x 3 = 15
50 x 30 = 1,500
500 x 30 = 15,000
500 x 300 = 150,000

What do you think we will do here?
5 x 4
5 X 4

What do you think we will do here?
5 X 4
5 x 4 = 20

What do you think we will do here?
5 X 4
5 x 4 = 20

What do you think we will do here?
5 X 4
5 x 4 = 20

What do you think we will do here?
50 x 4,000
200,000

You try!
40 x 100

What do you think we will do here?
4 X 1
4 x 1 =

What do you think we will do here?
4 X 1
4 x 1 = 4

What do you think we will do here?
4 X 1
4 x 1 = 4

What do you think we will do here?
4 X 1
4 x 1 = 4

What do you think we will do here?
4 X 1
4 x 1 = 4,000

You try!
400 x 200

You try!
4 00 x 2 00
8

You try!
4 00 x 2 00
8 0 0 0 0

You try!
400 x 200
80,000

What do you think?
60 x 300
18,000

Try all 4 on your board
9 x 400
60 x 900
1 x 70,000
200 x 9,000

Try all 4 on your board
9 x 400
3 , 6 00
54 ,000
1 x 70,000
200 x 9,000
7 0,000
1
60 x 900
, 8 00,000

How do you feel?
• Use your sticker chart to show me how you feel about multiplication with zeros?