LATER to Processor (on Abacus Abu): "Adding 6+5 was simple; let’s do something more complicated, like 23+9. Two 1-beads in the 10’s column and three 1-beads in the 1’s column represent 23. We represent 9 as 10-1. Two beads on the upper deck=10 (with pending carry to the 10’s column). Carry to the 10’s column and reset the upper deck of the current column which is also the 1’s column (with pending -1 on +10-1=+9). For that pending -1, bring down one 1-bead from the 1’s column (move it away from the middle bar). This is 23+10-1 or 23+9 or 32 (as read from the middle bar).

"To perform addition, move beads towards the mid-beam; to subtract, move beads away from it." (To be continued; write at The Tribune or adityarishi99@yahoo.co.in)

*We are sorry: Two pictures were missing in the abacus story last week. The corrected article is available on the Internet at www.tribuneindia.com. The published pictures show the final stages of the operation. The error is regretted.