Counting and Measuring with Lego: Preschool Maths Game - Good way to visually compare numbers - I would suggest making the corresponding numbers (like 5 and 15 or 8 and the same color to help see the pattern relationship between the numbers and 15
Number Sense Craftivity - Students trace their hands, cut out & glue down onto paper, except for the fingers! Kids will love this because they will be using their paper fingers to count.
Is Duplo worth investing in or should you wait until they are ready for LEGO? We can answer that question!