Why do this
might be a challenge for younger learners but it
allows them to use and think about some of the mathematical facts
that they have learned. It is wonderful for paired or group
What are the possible numbers to go into the middle
If you put that number there what numbers are left to use?
Learners could be encouraged to return to the problem and to check
each of the conditions against their solution so that they can
prove why their solution works.
Many children will find it helpful to use a set of digit cards from
$0$ to $9$ so that they can be moved around.