<p>Using the Subtraction Strip Board, the child practices the equations of the subtraction tables 1-18. Natural wooden strips corresponding in length to the squares 1-18 are used to indicate the number to subtract from (minuend) and a set of blue strips are used to subtract with (subtrahend). A set of red strips is included for further explorations. The two sets of strips are stored in hardwood boxes. (For age 3-12)</p>