Thank you to all those of you who submitted solutions to Becky's Number Plumber problem.
Joshua sent us a particulary well-explained solution:If there is an even number in the feedback box the answer's unit digit will always be $6$.
Matthew and Hannah from Stanbridge point out that:The rule doesn't work if you put in $0$. The answer is $-4$.
Well done too to the following who sent in clear solutions:
Velina, Ben, Emily, Max, Alex, Matthew, Lucy, Paige and Ross from Ickford Combined School
Jasper, George, James and Ed from St Peter's College
Maya, Marlee, Ethan, Joshua, Samara and Taylor from Sylvan Park.
I wonder whether anyone found any numbers that work in a similar way? Do let us know if you've discovered something interesting.