Math Abacus (13 Rods)

The abacus is often used to teach arithmetic to blind students. It can be used to perform addition, subtraction, multiplication, and division. It also has nonmathematical uses, such as keeping the running balance in your checking account, making a temporary note of a phone number, or tracking knitting rows in a complicated pattern. The abacus measures 1/2 × 3 × 6 inches and features thirteen rods with five beads each. A felt backing helps to keep the beads in place. Four of the beads on each rod are in the bottom section and represent one through four. The fifth bead in the top section represents five. The beads assume their value when they are pushed against the middle dividing bar.