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2-Digit by 2-Digit Multiplication | Math with Mr. J



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[Music]

welcome to math with mr j

[Music]

in this video i'm going to cover how to

multiply two digit numbers by two digit

numbers

and we have two examples that we're

going to go through together

in order to get this down so let's find

each product here

and remember product means the answer to

a multiplication problem

so for number one we have 39 times 24

and the first thing we need to do is set

this problem up

and we can do that by writing 39

times 24 when setting these problems up

just make sure that your places are

lined up meaning the 9 and 4

are lined up because they are both in

the ones place

the three and two are lined up because

they are both in the tens place

so the process that we're going to go

through essentially what we're going to

do we're going to do 4 times 39

and then 20 times 39 now i said

20 times 39 because the 2 in 24

has a value of 20. so let's go through

this process

and the first thing we're going to do is

4 times

9 which gives us 36.

now we carry our 3 to the tens place

there

next we do 4 times 30 and i say 4 times

30 because the 3 in 39

has a value of 30 but we can just think

of it as

the simple digits of uh four times three

here

so four times three is twelve plus that

three that we carried

is fifteen now i'm just going to drop my

one here because i don't have any more

places to carry that one to

so i am done doing four times 39 so i

can cross off the four because i'm done

with that

and i'm done with this three here

crossing things off when you're done

with it

helps you so you don't get confused with

any other numbers that we carry

later on in the problem now this next

step is very important

we need to put a zero here for when we

do

20 times 39 and we put that zero there

because the 2 in 24 has a value

of 20 so that 0 represents that

now we go through our process 2 times 9

is 18. so we put our 8 and carry

our 1. see why we crossed out that 3

earlier

so we don't get it confused with any

other numbers we carry

then we do 2 times 3 which is 6

plus that 1 is 7.

so we have four times 39 is 156

and 20 times 39 is 780.

now we add these two answers together to

get our final answer or product

so six plus zero is six five

plus eight is thirteen one plus one is

two plus that seven is nine

so we get a final answer of 936

so on to number two where we have 68

times 57

so let's line our problem up

and now we're ready to solve so we need

to do 7 times

68 and 50 times 68

7 times 8 is 56 carry our 5

7 times 6 is 42

plus 5 is 47

so we get 476. we are done with this 5

here

and we are done with this 7. now that

we're moving over to the 5

of 57 that 5 has a value of 50

so we need a 0 here

before we can continue on now we do

5 times 8 which is 40.

so we have a 0 carry the 4.

5 times 6 is 30 plus that 4 is 34 so i

put my 4

and there are no more places to carry

that 3

to so we can drop it there

and now we can add these partial

products those are called partial

products because they're

they are part of our final product so

add them together

six plus zero is six

seven plus zero is seven four plus four

is 8 and then we have our 3 there

so 3 876

is our final product there so there you

have it there's how you multiply

two digit numbers by two digit numbers i

hope that helped

thanks so much for watching until next

time

peace