 Doing a sorting activity is a great way to help a child learn to compare sizes. You can give the child some paper squares of three sizes, small, medium, and large, making sure there are a few of each size. Then you can say, let's sort these by size. We'll put all the small ones together, all the medium ones together, and all the large ones together. You can first show them how to do it for one of the sizes. Then they can try sorting the other sizes. Learning to sort by size will help improve a child's logical thinking.