Video Transcript
Making 100 with 10s
In this video, we’re going to
decompose, which is another way of saying “split up” the number 100 into multiples
of 10. And then, we’re going to model what
we’ve split up using base 10 blocks or 10 frames as well as equations.
This is 100 square. It’s a good way of representing the
number 100. Each row of the 100 square contains
10 little squares. We can tell this just by looking at
the numbers in the top row, can’t we? They go from one to 10. In fact, if we look at the numbers
at the end of each row, we can see how many squares we’ve got. This rectangle contains 10
squares. This rectangle contains 10, 20
squares.
This rectangle is an interesting
one because we’re not starting counting from one. So we can’t look at the last
number. Instead, we’re going to have to
count in 10s for each row. 10, 20, 30, 40. This rectangle contained 40
squares. Four rows of 10 means we have to
count in 10s four times. All the numbers that we get when we
count in 10s are called multiples of 10. Let’s split the number 100 into two
multiples of 10.
What we could do is fill some of
the rows with blue counters and then the rest of the rows with orange counters. There we go. We can say we’ve partitioned or
split up the number 100 into two parts. How many counters are in each
part? We’ve covered up all the
numbers. So, we’re going to have to count in
10s. There are 10, 20, 30, 40, 50 blue
counters. And this means there are 10, 20,
30, 40, 50 orange counters too. The two multiples of 10 that we’ve
split 100 into are 50 and another 50. 50 is a part, 50 is another part,
100 is the whole.
You know, we could show what we’ve
done here using base 10 blocks. 50 plus another 50 makes a total of
100. We could even write this as a
number sentence. 50 plus 50 equals 100. You know, we call this a number
bond to 100. It’s a pair of numbers that go
together to make a total of 100. Perhaps, the last time you came
across number bonds was when you thought about number bonds that make 10. It’s something that we’re taught
when we first start learning about addition.
Now, look at the number bond we’ve
made that adds up to 100. Is it very similar to a number bond
that makes 10? Yes, it is. If we know that five add five makes
10, then we can also say that 50 add another 50 makes 100. And do you know we can use all the
other number bonds to 10 to help us find pairs of multiples of 10 that make 100. If we know that six add four makes
10, we also know that 60 plus 40 makes 100. Let’s have a go at answering some
questions now where we’ve split up the number 100 into different multiples of
10.
Use the models to find the missing
numbers. Seven plus what equals 10. 70 plus what equals 100.
In this question, we can see two
additions that have been modeled. To start with, they might look very
different. The first addition shows two groups
of ones cubes being added, but in the second picture we can see two groups of tens
blocks being added. They might look different, but
there is a link between them. And we need to use these models to
find the missing numbers in the additions. To start with, let’s look at the
first part–whole model.
That we’re making by adding these
two parts together is 10. The first part that the number 10
has been split into shows one, two, three, four, five, six, seven. Seven ones are worth seven. Now, we can see where the first
addition comes from. Seven plus what makes a total of
10. Now, maybe, you know your number
bonds to 10 and you know which number goes with seven to make 10. Well, even if not, we can count the
number of ones cubes in the other part. There are three. Seven plus three equals 10.
Now, let’s look at our second
model. And we did say that these two
models are linked. Instead of making 10, this time,
we’re making 100. And just like before, the whole
amount has been split into two parts. Both groups contain 10s blocks. So, we know that the number 100 has
been split into two multiples of 10. There are seven 10s blocks in our
first part. That’s the same as 10, 20, 30, 40,
50, 60, 70. 70 plus what equals 100? Well, we need 10 lots of 10 to make
100.
We already have seven lots of
10. And we know from before that seven
and three make 10. So, we’re going to need another
three lots of 10. 10, 20, 30. 70 plus 30 makes 100. If we know what goes with seven to
make 10, then we can work out what goes with 70 to make 100. Seven plus three equals 10. 70 plus 30 equals 100. The two missing numbers are three
and 30.
Fill in the missing number.
The missing number in this
problem is one of the parts in a part–whole model. The whole amount is worth
100. And this has been split into
two parts: 80 and something else. So, we could say 100 is equal
to 80 plus what. To help us find the answer, we
could use 10 frames. Now, one 10 frame on its own
only shows 10, but we can use it to make a fact that can help us. We know that 10 can be split
into eight and two. Eight plus two equals 10.
Now, we know the number 100 is
made up of 10 10s. So, to show the number 100,
we’re going to need 10 10 frames. In our question, the number 100
has been split up into 80 and another number. How many 10s is 80? 10, 20, 30, 40, 50, 60, 70,
80. Eight groups of 10 make 80. But we don’t want eight groups
of 10. We want to make 10 groups of
10. And this is where our number
fact comes in useful. We know that eight and another
two make 10. And so, 80 and another 20 make
100. 80 is a part, 20 is a part, and
the whole is 100. The missing number from our
part–whole diagram is 20.
So, what have we learned in this
video? We’ve learned how to decompose or
split up 100 into multiples of 10. We’ve also learned how to model
what we’ve done using base 10 blocks, 10 frames, and equations.
