4th Grade Go Math Chapter 3

4th Grade Go Math Chapter 3

Multiplying 2-digit numbers

• Multiply by 10s

• Estimate products

• Box method

• Partial products (break it up)

• Regrouping (old school)

Multiply by 10s

When we're multiplying by tens we can focus on multiplying the first digits, and then slap on the zeros after.

64 x 10 = 640

23 x 100 = 2,300

We can also do this if both digits end in zero.

60x20=1200

30x50=1500

Or, if just one ends in zero

12 x 20 = 240

17 x 30 = 510

Multiple Choice

50 x 50 = 2,500

• True

• False

Multiple Choice

60 x 30 = 180

• True

• False

Estimate Products

When we estimate products we round each of the two factors, and then we multiply them.

24 x 38

20 x 40

800

Multiple Choice

Estimate the product 88 x 51 =

• 4,000

• 4,488

• 4,500

Multiple Choice

Estimate the product 29 x 32 =

• 928

• 600

• 900

Box Method

• Put the factors on either side

• Write 64 x 22 as 60 4 and 20 2 on each side

• Multiply each box

• Add the top boxes

• Add the bottom boxes

• Add the final two numbers to get the final product

Multiple Choice

Finish the problem in the picture.

• 1016
• 916
• 786
• 816

Multiple Choice

What goes in the yellow box?

• 60

• 160

• 1600

• 1200

Partial Products

REMEMBER you can only break up one of the two factors when you multiply with partial products.

24x12 I can break up one one of the two factors. I choose 12.

24x10 =240

24x2=48

Then, I add up both products.

240+48= 288

Multiple Choice

Find the answer to 243x9 using partial products

• 2128

• 2187

• 2817

Multiple Choice

Which of these multiplication problems is a part of 5,812 x 7?

• 7 x 100

• 7 x 5

• 7 x 800

• 70 x 2

Regrouping (old school)

• multiply both top digits by the ones digit on the bottom

• carry if you have to

• put a zero in the ones place on the second row

• multiply both top digits by the tens digit on the bottom

• add up both of the product rows to get your final product

Multiple Choice

54 x 52

• 2808

• 2788

• 2800

• 2728

Great work!

Now, take out your chapter 3 book

Open to the practice test at the back

Choose one page of the test

Complete that page for your independent work today!