Video Transcript
Subtracting from Three, Four, and
Five
In this video, we’re going to learn
how to use pictures and subtraction equations or number sentences to show all the
different ways to take away from the numbers three, four, and five. Let’s start by thinking about the
ways that we could subtract from the number three. Here, we have three football fans
cheering their team on. We could use a five frame to model
our group of supporters: one, two, three of them. If we were drawing a part–whole
model, we’d write the number three at the top because the whole amount, the whole
group, is worth three.
Now, what are the different ways we
could take away from the number three? Well, to start with, we could just
take away one. Let’s imagine one of the football
fans gets a bit fed up with the game. He decides to go home before the
end. We could also show this subtraction
using our counters. If we start with three counters and
we take away one counter, how many counters will we have left?
Well, if we look at both of our
pictures, we can see the answer. There are one, two football fans
left. And in our five frame, we can see
one, two counters left. By taking away one, we split up the
group of three into two parts. And you know we can complete our
part–whole model to show these two parts. Three take away one left us with
two because one and two go together to make three.
We could even write our subtraction
as a number sentence or equation. We started with three, and then we
took away one. So we need to use the subtraction
symbol, this little line, followed by the number we took away. Three take away one equals, which
means is the same as, two. That’s one subtraction we can make
by taking away from three. What else can we do?
Let’s put our group back
together. So we can start with three again,
and we’ve tried taking away one. Let’s try taking away two. This time, we can imagine two of
our football fans get fed up with the match, and they both decide to go home. The subtraction we need to work out
now is the answer to three take away one, two. What goes together with two to make
three?
Well, we know that two and one more
make three. And that’s how we know that three
take away two equals one. We found two different ways to take
away from three. Three take away one is two, and
three take away two equals one. We’ve tried to find all the
possible subtractions by starting with one and then taking away one more.
Let’s have a go at practicing this
skill of taking away one and then one more to find all the different possible ways
now of subtracting from four and five. We’ve got a couple of questions
that are gonna help us to do this.
Find the missing equation. Four subtract one equals three. What? Four subtract three equals one. And we have five possible
answers. Four subtract three equals two. Four subtract two equals one. Four subtract three equals one. Four subtract two equals two. Or four subtract one equals
three.
In this question, we’re given some
ten frames. And next to each of the ten frames
is an equation or a number sentence. Well, next, in nearly all of the
ten frames, the middle ten frame has a missing equation. And we’re asked to find the missing
equation or number sentence. So let’s have a look at our ten
frames. What do they show us?
In the first ten frame, we can see
four green counters. So we’re starting with four. But one of the counters has been
crossed out. We’ve taken it away. What are we left with if we have
four and we take away one? We’re left with one, two,
three. And we know this is true, don’t
we? Because one and three are a pair
that go together to make four. Four take away one equals
three.
If we look at our last ten frame,
we can see that we’ve started with four green counters again. But this time, we’ve taken away
three of them. How many are left? Or, in other words, what number
goes together with three to make four? We know that three and one make
four. And that’s why we can say four take
away three leaves us with one. So what’s our missing equation?
Again, we’ve started with four
green counters. But the diagram shows that we need
to take away two. The subtraction we’re looking for
is four take away two. Now, if we look at our possible
answers, we can see this is written twice. Four take away two equals one, and
the four take away two equals two. Which is correct? What number goes with two to make
four?
We know that two and another two
make four. And so if we take away two from
four, we’re going to be left with two. Our missing equation is four take
away two equals two.
Find the missing equation. Five take away one equals four. Five take away two equals
three. What? Five take away four equals one.
In this problem, we’re shown four
pictures of ten frames, and they each show a subtraction. If we look at each ten frame, we
can see that the top row of each one is completely full. In other words, we’re starting with
five counters every time. That’s why when we look at the
number sentences or equations that follow these pictures, we can see the number five
is first. It’s the number we’re starting
with. But can you see we don’t have a
subtraction for our third picture. It’s missing. And the question asks us to find
this missing equation.
Well, we know which number to start
with. Just like all the other pictures,
we have five green counters to begin with. If we look at our first picture, we
can see that we’re taking away a small amount of counters, one. Then in the second picture, we’re
taking away one more than this. We take away two. By taking away one more each time,
we know that we can find all the different possibilities. So if we take away two in this one,
in the next calculation, we need to take away three.
Let’s check the diagram to see if
this makes sense. Yes, we can see that we’re taking
away three out of our five counters. All we have to do now is to think
about what the answer is going to be. What number goes with three to make
five? We could imagine a cube train
containing five cubes. And if we break it apart so that
there are three in one group, we know that there’ll be two in the other group. Five counters take away three
counters leaves us with two counters. And we can see in our last equation
we take one more again. Five take away four this time
equals one. We know that three and two go
together to make five. And so our missing equation is five
take away three equals two.
What have we learned in this
video? We’ve learned how to use pictures
and subtraction number sentences or equations to show all the different ways to take
away from three, four, and five.
