If you're looking for some more challenging tasks for pupils who have a good grasp of the concept of common multiples, try this Year 6 Common Multiples Discussion Problem pack! It contains two tricky, open-ended problem-solving questions, which we've designed to promote mathematical talk and the application of common multiples knowledge.
This resource obviously works well as a group task in school, but can be done by individuals, or with an adult as the discussion partner, and works at home as well. The pack also comes with an example answer sheet, so that you or the children have an easy way to check that they're on the right track!