Learning Resources Sand Moulds - Numbers and Operations. Early learners can get hands on with basic maths skills with these plastic numbers and operations sand moulds. These sand resources are ideal for encouraging tactile learning and reinforcing fine motor skills whilst practicing early number skills. Use in the sand tray or outdoor environments. Set of 26 moulds includes 2 of each number (0-9) and six maths operations signs. Moulds measure 7.5 x 0.5 cm thick. Mesh storage bag included. Suitable for ages 3 years and above.