Online Abacus and Soroban

Each lower bead is worth 1 and the upper bead 5; only beads pushed against the bar count. A number is set from left to right, one rod per place: 7 is the upper bead and two lower ones, 47 is four lower beads on the tens rod and 7 on the ones rod. The dots on the bar mark the ones rod and every third place, so thousands and millions are easy to find.

They are the formulas of abacus math for when the beads you need are not free. A small friend completes a number to 5: +4 = +5 − 1 — bring down the upper bead and take one lower bead away. A big friend completes it to 10: +7 = +10 − 3 — take 3 away on this rod and add 1 on the rod to the left. When the big friend itself needs a small friend, both work together: 6 + 7 = 6 + 10 − 5 + 2.

In the two-finger method the thumb only pushes lower beads up to the bar, and the index finger pushes them down and moves the upper bead. When the upper and lower beads go to the bar together — say for 6 or 7 — you pinch them with both fingers at once. The step-by-step solution names the finger for every move.

Each wire is a place: the bottom one is ones, above it tens, hundreds and so on. A number is set by sliding beads to the left and cleared by sliding all of them back to the right. The 5th and 6th beads are dark so five is seen at a glance. When a wire runs out of beads you carry: to add 8 to 7, move 2 beads back to the right on the ones wire and 1 to the left on the tens wire — that makes 15.

The Chinese suanpan has 2 upper and 5 lower beads on a rod, so one rod can hold up to 15, which suited old weight units. The Japanese soroban cut that to 1 + 4: every digit is set in exactly one way, which is why mental arithmetic is taught on it. The Russian schoty lie horizontally with 10 beads on a wire, counted by sliding them to the left.

It separates rubles from kopecks and was historically used to count polushkas — quarters of a kopeck. Turn on «Rubles and kopecks» in the settings: the quarter wire and two kopeck wires appear and the total is shown with kopecks.

In flash anzan numbers appear one after another for a fraction of a second and the learner adds them in their head by picturing the abacus. With flash cards a picture of an abacus is shown for a moment and you name the number. In the trainer the pace goes from 0.3 to 4 seconds, and the answer is typed or set on the abacus.

In the «Sheets» tab choose the formulas, digits and number of terms and press «Download PDF»: a page holds 20–80 column examples with answer boxes, and the answer key comes on a separate page. The same tab makes flash card sheets and blank abacus pictures to draw a given number on.