hey there it's kayleigh in this lesson we're going to do some subtraction
of bigger numbers and use regrouping make sure you've already learned
how to do regrouping with two digit numbers before we jump into this one
let's start off with a simpler problem to remind ourselves how to do regrouping this problem says
44 minus 27. do you know how to do it i'm going to start by writing our problem out vertically
so we have 44 minus 27 remember we have to be really careful about lining up our tens place
and our ones place we can expand these numbers out to make it really clear so this is really saying
40 plus 4 minus 20 plus 7 right that makes sense 44 is 40 plus 4 and 27 is 20 plus 7. so let's
start here with this expanded version we need to subtract 7 from 4 can we do that no right because
4 is a smaller number than seven so what do we need to do yeah we need to borrow or do regrouping
so if we go over to our neighbor here in the tens place we have a 40 here now i'm going to borrow a
10 from 40 so that means i'm subtracting 10 from 40 so this becomes 30 and then i'm taking that 10
and i'm going to add it so plus 10 here to my four so now this 4 becomes 14. and now i can subtract
14 and 7 which gives me yeah 7 and then here in my tens column i can subtract 30 minus 20 is 10.
so my answer is 10 plus 7 and that's equal to 17. perfect now let's try to do the same thing
with our unexpanded version right over here so i start in my ones column right
and i have four minus seven but can i subtract that no how come yeah seven is bigger than four
right i need my bigger number on top so i'm going to go next door over to my tens place
and from this number i'm going to take what yeah a 10 because this is really 40 remember it's 40
and i took a 10 to give me 30. but over here i'm just going to write a 3 because a 3 in the tens
place means 30 perfect and then i'm adding that 10 here to my ones column so this 4 becomes 14.
so now i have 14 minus seven that gives me seven then here i have three minus two and that gives me
one so i get 17 again which i should get right i should have matching numbers good work now
we're going to take it up a notch here we have 528 minus 364. so to start i'm going to write this out
vertically how many columns should i have yeah that's right i should have three columns right
i have my hundreds column my tens column and my ones column and then i line up my 364 under that
364. so that's my subtraction problem but let's write this out again
in expanded form so this is saying 500 plus 20 plus 8 all minus 300 plus 60 plus 4. okay
so let's start here we're subtracting from our ones column first so we have
eight minus remember our subtraction sign is over here eight minus four that gives me four
perfect and then i move over to my tens column here and i have 20 minus 60. ugh can i do that
no right because 60 is a bigger number than 20. i need my bigger number on top so what do i do
yeah i'm going to go next door to my hundreds place and i see i have 500 here now i'm gonna
borrow what not a ten this time i'm borrowing an entire hundred and i'm going to give it
to my tens place so if i'm borrowing a hundred this 500 becomes 400 and then i'm going to add
this 100 over here to my tens place so this number becomes not 20 but 120. now 120 minus 60 gives me
60 okay now i can go over to my hundreds place and i have 400 here remember because i borrowed
my hundred so this is 400 minus 300 that gives me 100. and if i add all these up i get 100 plus
60 plus 4 gives me 164. perfect now let's try to do the same thing over here with our unexpanded
version so we start with our ones place here right that's where we always start our subtraction
eight minus four that gives me four and i go to my tens column two minus six can't do that
right the two is smaller and it's on top so i'm going to go over to my hundreds place here i'm
going to borrow so i'm taking this this is 500 i'm borrowing a hundred remember so this becomes four
since it's in the hundreds place here this means 400 remember it means 400 and then i'm adding
that 100 over here and so this becomes 12 okay so i could have crossed out my 2 and i write a
12 up here and this is telling me that i have 12 in the tens place so 12 minus 6 that gives me 6
and i have 4 minus 3 that gives me 1. and look at that my 164 here matches my 164 from over here
perfect okay we have one more example all together this one says 1334 minus 156. so i have four
digits here so let's figure out how we're going to line these up starting with my top i have 1334
and then i'm subtracting i don't have a number in my thousands place so i put the 1 in the hundreds
place so 1 5 6 156 and we're subtracting that so let's try this one without rewriting
into expanded form so we're going to do it right here so we'll start with our ones column
we have 4 minus six can we do that nope we have to borrow right so i'm gonna go next door
i have a three here so i'm gonna take one here for my tens place this becomes a two and i'm giving a
10 here to my ones place so this 4 becomes 10 plus 4 which is 14. so 14 minus 6 that will give me 8
perfect so i'm going to my tens place let's see i have 2 minus 5. can i do that
no right 2 is smaller so i need to go next door to my hundreds place i have a 3 here so from my 3
i'm going to take 100 so now i have a 2 in the hundreds place and i'm giving a hundred
to my tens place so i'm putting a 1 here this tells me i have 12 in the tens place 12 minus
5 that gives me 7 and then i have 2 minus 1 here in the hundreds place which gives me 1 and then
i have 1 minus this is just a 0 there's nothing here so one minus zero is one so our answer is
one thousand one hundred and seventy eight good job great work using regrouping to subtract
three digit numbers you're ready to practice on your own have fun and remember to always be
clever