The style of abacus, pictured here, fitst made of bamboo rods and beads dates back to about 500 B.C. Each of the two beads above the crossbar has a value of 5, and each of the beads below the cross- bar has a value of 1. Computation is carricd out by movinThe style of abacus, pictured here, fitst made of bamboo is and beads, back to about soo dates B. C. Each of the two beads above the crossbar has a value of 5, and earh of the beads below the crossbar has a value of 1. Computation is carried our by moving the beads. Each of the rods represents a different position in the place- value system. Illusrtation(1) shows the correct arrangement of beads to represent 8,305 and illustration(2) shows 342,961.