This problem would make a good short challenge, for example
first thing in the morning as you are taking the register. It
requires some logical thinking and quickly leads to a
generalisation.
Key questions
Is there a way to make sure both 'slots' of the toaster are
always being used?
Possible extension
Many children will be able to find a general rule for the
minimum length of time taken for any number of slices of
toast. Can they explain why the rule always
works?
Possible support
Using something to represent the slices of bread might help,
for example, playing cards which are different on each side so that
it is easier to keep track of what has been done.