### Video Transcript

Liam is learning strategies to
divide. He finds that 21 divided by three
equals 12 divided by three plus what divided by three. What number is missing from his
equation? Use his equation to write the
missing addition expression: 21 divided by three equals what plus what.

This array has three rows. And there are seven hearts in each
row. Liam is working on 21 divided by
three. This means that there are 21 hearts
altogether. Seven times three equals 21; 21
divided by three is seven. Liam has split his division into
two parts. He say’s that 21 divided by three
is equal to 12 divided by three and something divided by three. We have to find the missing
number. If we look closely at the array, we
can see the each row has pink hearts and blue hearts. This must be why Liam has two
divisions. There are four pink hearts in each
row and three blue hearts. So each row has four pink hearts,
and there are three rows. Four lots of three or four times
three is 12.

This is where Liam got the division
12 divided by three. This is for the pink hearts. Four times three is 12. 12 divided by three is four. There are three blue hearts in each
row. There are three rows of three,
which makes 9 — 3, 6, 9. So the missing number must be
nine. There are nine blue hearts
altogether. They’ve been divided into three
equal groups, and each group contains three hearts. So the number missing from his
equation is number nine. 21 divided by three is equal to 12
divided by three and nine divided by three. 12 plus nine is 21. So altogether, we have 21 divided
by three.

The second part of the question
asks us to complete the missing addition expression. We need to find the two missing
numbers. 21 divided by three equals what
plus what. We already know that each row of
hearts has four pink hearts and three blue hearts. And we know that 21 divided by
three is seven. So our two missing numbers need to
add together to give us a total of seven. Four plus three is seven. So 21 divided by three equals four
plus three. The missing numbers in the addition
expression are four and three. Four and three makes seven, and 21
Divided by three is seven. Well, the answer to the first part
of the question is nine. And the answer to the second part
of the question is four plus three.