This is a great way to get kids started on writing their own "number puzzles." This can be differentiated by using various 100s charts (1-100) (100-200) (200-300) (300-400) (etc.). The kids can also make their own puzzles with boxes in all directions.
Here's a comparison activity for length. Students receive 5 different colored strips of construction paper that are 1"x6" long. Students cut each strip into 2 unequal pieces and glue them onto the appropriate column of the chart.