Doug Wilson, age 11, of Pocatello, Ida., for his question:

HOW DOES AN ABACUS WORK?

An abacus is made up of a frame containing columns of beads. It is an ancient device used in China and other Asian countries to perform arithmetic problems. It can be used to add, subtract, multiply and divide and to calculate square roots and cube roots.

The beads, which represent numbers, are strung on wires or narrow wooden rods attached to a frame.

A typical Chinese abacus is made up of 13 columns of beads. A crossbar separates the beads. Each column has two beads above the crossbar and five below it. Each upper bead represents five units and each lower bead equals one unit.

The first column on the right is the ones column. Second column is the tens, while three is hundreds and four is thousands. Number five is 10 thousands with columns continuing as 100 thousand, millions, 10 millions, 100 millions, billions, 10 billions and 100 billions. The 13th column is trillions.