Why do this
makes interesting use of multiplication facts.
The challenge can easily be used without the connection
with fractions and by just dealing with the denominators.
Tell me about the numbers you've found.
For more advanced/experienced/older pupils, challenge them to
find the number of different combinations according to:-
the number of fractions that are
allowed to be multiplied together;
the range of numbers that are
allowed to be used.
If you pursue this you may come across the addition of
triangular numbers [to make pyramid numbers] and then
the addition of these [pyramid] numbers, and so on!
Calculators may be supportive for those pupils without fast
recall of facts.