4th Grade Math

Multiplying 2-digit by 2-digit Numbers

Using the Area Model / Box Method

Slide 1

Here's the Problem

Let's go with 23 x 45

Slide 3

Expanded Form

23 becomes 20 + 345 becomes 40 + 5

page 4

Drawing Time!Draw a window with 4 panels.20 and 3 go on the top40 and 5 go on the side

Okay, Let's Multiply!

❖ The top left square...

❖ Is under the 20...

❖ And beside the 40...

❖ So multiply 20 x 40

❖ 800 in the 1st square

Square 2

❖ The top right square...

❖ Is under the 3...

❖ And beside the 40

❖ Multiply 3 x 40

❖ 120

Down on the Corner

❖ Bottom left square...

❖ Under the 20...

❖ Beside the 5

❖ 5 x 20

❖ 100

The Last Panel

❖ The bottom right square...

❖ Is under the 3...

❖ And beside the 5

❖ 3 x 5

❖ 15

How much are those numbers in the Window?

❖ These 4 numbers are the partial products

❖ Add them together to get the final answer

❖ Thanks to the commutative property the order that you add them doesn't matter

❖ In this example, we are adding across first, then adding our two answers

Add it up!

❖ Adding the top row

❖ 800 + 120

❖ 920

Bottoms Up!

❖ Adding the bottom Row

❖ 100 + 15

❖ 115

Summing it Up

❖ Add the two sums together

❖ 920 + 115

❖ 1,035

Almost the last page

This is it! 23 x 45 = 1,035

This is the last page

I hope this helpsThe end(Told you it was the last page)