Video Transcript
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.
