3.1 Multiplying by 10s, 100s, 1000s

3.1 Multiplying by 10s, 100s, 1000s

Let's see how much you remember about multiplying by 10s.

Multiple Choice

What is 10 x 10?

• 1

• 10

• 100

• 1,000

Poll

How well do you understand multiplying by tens?

• I got this! I rarely make a mistake.

• I understand, but I make a mistake once in a while because I go too fast.

• I kind of get it , but not quite.

• I don't understand how to multiply by tens.

So, what's the rule to follow when you multiply by a number that is a product of 10 (ends in a zero)?

What is the rule to follow when you multiply by a number that is a product of 100 and another number (ends with 00)?

Let's try a few problems....

Multiple Choice

What is 300 x 5?

• 1,500

• 800

• 305

Multiple Select

Check all that apply:

4,500 =

• 9 x 500

• 900 x 5

• none of the above

Poll

So, when you multiply by a number that is a "hundred" (for example, 4 x 400), you multiply by the non-zero numbers, and then add the zeroes.

4 x 400 = 4 x 4 x 100 = 16 hundreds or 1,600 In standard form.

How confident are you in doing multiplication with hundreds?

• Totally confident

• I get it but need more practice

• I understand a little

• I don't understand

In today's lesson we are going to multiply by numbers that are both products of tens, hundreds or thousands.

Multiple Choice

It's the same concept. Let's look at the multiplication a different way.

30 x 20 is the same as 3 x = 10 x 2 x 10.

We can move the factors around, because multiplication is commutative.

3 x 10 x 2 x 10

=3 x 2 x 10 x 10

= 6 x 10 x 10 = ?

• 60

• 600

• 6,000

Multiple Select

What are different ways to represent 80 x 40?

Check all that apply.

• 8 x 10 x 4 x 10

• 8 x 4 x 10 x 10

• 32 x 100

• 32 x 10 x 10

• 3,200

Multiple Choice

250 x 100

• 2,500

• 25,000

• 250,000

• 2,500,000

Multiple Choice

300 x 300

• 90

• 900

• 9,000

• 90,000

Multiple Choice

90 x 4

• 36

• 360

• 3,600

Multiple Choice

1,000 x 80

• 80

• 800

• 8,000

• 80,000

Multiple Choice

35 x 20

• 70

• 700

• 7,000

Multiple Choice

60 x 200

• 120

• 1,200

• 12,000

• 120,000

Multiple Choice

10 x 75

• 75

• 750

• 7,500

• 75,000

Multiple Choice

70 x 500

• 350

• 3,500

• 35,000

• 350,000

Multiple Choice

200 x 30

• 60

• 600

• 6,000

• 60,000

Multiple Choice

50 x 40

• 20

• 200

• 2,000

RECAP

When multiplying by tens, hundreds, thousands (and any multiple of 10):

• FIRST, multiply the non-zero numbers

• THEN, count the number of total zeros in the FACTORS

• LAST, put the number of zeros onto the product that you found at the start

What's Next

During Independent Work time, make corrections to your test (in journal or loose-leaf, solving and showing steps) and submit via photo. Details are posted in Google Classroom.