This activity 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.