Why do this problem?
This short problem
could be used to start a lesson or fill a gap made by those who finish early. It will promote thinking about numbers and offers opportunities to practise multiplication and division.
What results can you find obeying these rules?
Why don't you put all your answers in order?
What things do you notice about your different results?
Why do you not get any divisions by $5$?
Does it help to multiply by $1$? If not, why not?
Learners could make the largest number that they can using the same rules, and then as many results in between as possible.
Using a calculator will help some children.