Use the following part–whole model
to find 84 divided by three.
Often, we can use times tables
facts we already know to help us with a division. But do you know a times tables fact
that’s going to help you find 84 divided by three? It’s quite a large two-digit number
we need to divide, isn’t it? And that’s why in this question
we’re shown how to split it up into smaller parts to help us. The whole amount in the part–whole
model that we’re given is 84; it’s the number we’re dividing. And we can see it’s been split into
two parts, 60 and 24. Now, often when we break apart
two-digit numbers to make them easier to work with, we split them up into their 10s
and ones. But with this calculation, it would
have meant splitting up the number into eight 10s or 80 and four ones.
But if our part–whole model had
shown 80 and four, we’d have found it really difficult to divide by three. Neither of these parts are
multiples of three. And that’s why we’ve been given
this particular part–whole model to help us. Both 60 and 24 are multiples of
three. And they’re also multiples of three
that we already know facts for. So we can divide each part by three
to help us find the overall answer. First of all, how many threes are
in 60? Well, this is still quite a large
number, but we know a fact that can help us. We know that 10 threes are in
30. 30 divided by three equals 10. And so, if we double 30 to get 60,
we double the number of threes that we have.
60 divided by three equals 20. Now we need to divide the second
part by three. How many threes are there in
24? Three, six, nine, 12, 15, 18, 21,
24. There are eight threes in 24. We found out there are 20 threes in
60 and eight threes in 24. And 20 plus eight equals 28. We’ve used the part–whole model to
find that 84 divided by three equals 28.