adding with numicon What to do Try this What’s in my tray? activity to support simple addition with Numicon. What to do Split the tray into three columns- use masking tape. Draw out the mathematical symbols on the card and cut out. Fill in the first two digits with the numicon pieces. Let your child find the answer by using the numicon pieces they have in front of them. Challenge: Leave a space for a missing number and see if your child can solve the addition calculation.