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4th Grade Mathematics - Lesson 3: Multi-digit multiplication using the Area Array Model



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hi this is Taylor Hummel and welcome

back to math class today I'm going to

show you a little bit about one of the

strategies I'm going to be using to

teach your children about multi digit

multiplication

it's a little different from what you

were taught in school but stick with me

I think it's a really good strategy okay

so today we're going to look at using

the area of Ray model to help solve

multi-digit multiplication problems I

know that some of us were taught in

school how to use the regrouping instead

of the problem this way but in fourth

grade we have a lot of students that are

still visual learners and so I want to

give them something visual to make this

a little bit easier so the first thing

I'm going to do is I'm going to create

this box and I have four boxes because I

have four numbers over on this side so

if I had had one more number up here I

would have done three boxes going down

and two across so I put fifty tens up

here and for once again we're using that

expanded form of writing the numbers

that we learn in our place values at the

top I have one ten and eight ones and

then I'm going to multiply a crime what

I'm going to do is start with

multiplying these two numbers now

instead of multiplying 50 times Ted I

actually is going to multiply five times

one which we know is five and then I'm

going to add these two zeros and again

that's using our place value that we

learned in our lesson before this then

I'm going to go 4 times 1 which we know

is 4 and I've got one zero so I'm going

to add that then I come over here and

I'm going to do 5 times 8 which I know

is 40 and I'm going to add my 1 0 then I

have 4 times 8 which is 32 and I'm not

going to add any zeros because I don't

have any zeros there ok now that I've

got my boxes filled out we're going to

break them down here

okay so for some of the students I might

actually say go ahead and just put your

addition signs between each box to

remind you of what your next step is so

our next step is we're going to pull

everything down so you've got the 500

the 440 and 32 then we add them all

together so you've got 2 4 & 3 makes 7 5

& 4 makes 9 so our answer is 972 and

that is how you use the area in a Ray

model using a visual technique versus

the mental math technique that you use

in the partial products or the

traditional model right until next time

this is Taylor Hummel and I'll see you

in math class