Age 7 to 11
Remember the relationship between 'one times' and 'ten times' and 'one hundred times' a number. For example, 5 x 1 = 5 and 5 x 10 = 50 and 5 x 100 = 500.
You could begin by making both sides of the equation equal to 100, then 200, then 300 and so on.
Is there more than one way of completing the equation for each total? Can any of them be made in lots of different ways?