Video Transcript
Fill in the blank: 1,366 plus 353
equals what.
In this question, we’ve got two
large numbers to add together. We’ve got a four-digit number and a
three-digit number. Now, if these were simple numbers
like perhaps 2,000 and 400, we could look at a calculation written horizontally like
this and just work out the answer in our heads. I don’t think we could describe
these numbers as particularly simple, could we? We can’t just look at them and see
what the answer is. We’re going to have to use a
strategy to help us. And when we’re adding two numbers
like this, it’s going to be important that we keep track of the ones, the tens, the
hundreds, and the thousands. To do this, we can make sure that
that digits in both of these numbers are written in columns. We call this the standard written
method.
Our first number, which is 1,366,
is made up of one 1,000, three 100s, six 10s, and six ones. Can you see by writing it in a
place value grid like this, we’ve put each digit in the correct column? Now we’re adding 353. Is this right? It’s not, is it? 353 is a three-digit number, and we
need to make sure those three digits are in the correct place. They’re not at the moment. Let’s try again. 353 is made up of three 100s, five
10s, and three ones. That’s better. So although we’ve set out our
numbers in a place value grid, this is really what the standard written method looks
like: numbers written on top of each other so that the ones digits, the tens digits,
the hundreds digits, and the thousands digits are all separate.
Now, before we use this written
method to find the answer, let’s model our two numbers using place value counters
just so that we can show what we’re doing. 1,366 plus 353. Let’s start by adding the ones
digits. 1,366 has six ones, and 353 has
three ones. And six plus three equals nine. So we know our answer is going to
end in a nine. Now we need to add our tens
digits. 1,366 has six 10s, and 353 has five
10s. By the way, can you see how it’s
much harder to spot those two tens digits if we were reading our calculation across
the page? It’s so much easier when we write
it vertically, isn’t it?
But we’ve got a bit of a problem
here because we know that six plus five is 11, so six 10s plus five 10s equals 11
10s. And we know that each place in a
number can only have one digit in it. We can’t write 11 10s. We’re going to have to show our 11
10s a different way. We’re going to have to regroup
them. We can take 10 of our 11 10s and
exchange them for one 100. It’s important to see we haven’t
changed our total at all here; one 100 and one 10 is exactly the same as 11 10s. We’ve just shown it a different
way.
Onto the hundreds digits, 1,366
contains three 100s, and so does 353. Now we know 300 plus 300 equals
600. But we need to remember to include
the one 100 we’ve regrouped too. It’s often easy to forget this. The total number of hundreds that
we have is seven 100s. And a nice easy one to end with:
our second number doesn’t have any thousands, so all we have is the one 1,000 in our
first number. We found the total of these two
numbers by using the standard written method. And our place value counters helped
us to see what to do. When we made a total that was more
than nine in one of the columns. We regrouped and we exchanged 10
10s for one 100. 1,366 plus 353 equals 1,719.
