Video Transcript
Subtract two 10s and three ones
from 437. Hint: Use the place value blocks if
you need to.
In this question, we need to
subtract or take away a number from 437. And it’s interesting because the
number that we need to take away isn’t written as a numeral; we’re told it in terms
of the number of tens and ones that make it up. We’re told to take away two 10s and
three ones. Now we know that a number that has
two 10s is going to be twenty something. And if it has three ones, it’s the
number 23. And to help us solve the problem,
we can think about the number 437 like this. In other words, we can think of its
place value. It has four 100s, three 10s, and
seven ones. And can you see that the way that
we’ve written these numbers on top of each other like this, it shows the hundreds,
the tens, and the ones really clearly in separate columns?
That’s why if we write a
subtraction like this, we call it column subtraction. And it’s a method we can use to
find the answer really quickly. Perhaps, you notice over here we’ve
already got our column subtraction written out for us. So let’s use this method to help us
find the answer. And we’re given a hint to use the
place value blocks if we need to. So what we’ll do as we’re working
out the answer using column subtraction, we’ll take away some of the place value
blocks. And we’ll sort of mirror what we’re
doing in the column subtraction with the place value blocks; it’ll help us
understand it.
Now we always start with the
smallest value place when we’re doing column subtraction. So we’re going to start with the
ones. And we’re told that we need to take
away three ones. And we know that 437 has seven
ones, so we’re beginning with seven ones, and we’re taking away three of those
ones. This is where perhaps we could use
our place value blocks to show what goes on. We’re gonna take away one, two,
three. Can you see how many we’re left
with? Seven ones take away three ones
leaves us with four ones. So we know whatever answer we’re
going to get at the end of this, it’s going to have four ones.
Next, we move on to the tens. And we need to take away two
10s. And we can see that 437 has three
10s. If we look across at our place
value blocks, we can see there’s three 10s. So let’s subtract two of them: one,
two. Of course, three 10s take away two
10s is only going to leave us with one 10. So now we can see our answer is
going to have one 10 and four ones. It’s going to be something and
fourteen.
Now if we look at our column
subtraction, we can’t see any hundreds we need to take away. We were only asked to subtract a
number of tens and ones, weren’t we? So we started off with four 100s
and we’re going to end with four 100s too. And you should be able to see that
this three-digit number that we have as our answer is exactly the same as the number
of place value blocks that we have left over. There are four 100s, one 10, and
four ones. We’ve used column subtraction to
take away two 10s and three ones from 437. And we found that 437 subtract 23
equals 414.
