Learning Resources Wipe Clean Fact Family Boards. Children can easily identify the relationship between numbers with these wipe clean fact family boards. Set of 5 double-sided boards focus on addition and subtraction skills on one side, and multiplication and division skills on the other. Great for building a variety of primary maths skills including equations and problem solving. Boards measure 25cm H. Boards are wipe clean for repeated use. Suitable for ages 6+.