Why do this problem?
practises addition, subtraction, multiplication and division in an interesting and thought-provoking way.
What do all the numbers on the cake add to?
How many couples are there?
How can you use this total to work out the sum of the numbers on each couple's slices?
Learners who found the problem easy might like to try this one
A good place to start might be to suggest pupils work out (with a calculator if necessary) the sum of all the numbers on the cake.