How do I explain why the set of natural numbers (N) cannot be equivalent to one of its finite subsets? Hi Christina,You need to carefully understand what equivalent means  that there is a 11 correspondence between the sets. I think the best place to start is the Pigeon Hole Principle: if n+1 pigeons fly into n pigeon holes then at least one pigeon hole contains two pigeons. How does this help with your question if the finite subset has n elements? Penny
