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)
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