Kani Math
Cosmic Abacus
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One-digit addition and subtraction drills

Three single digits stacked in a column, added and subtracted straight on the beads — no complement rules, no borrowing.

  • 3 rows × 1 digits, add & subtract
  • About 6 min
  • Free, no account

Sample problems

Real problems from this drill, with answers. Nothing to install, no account, no email — work them on paper, on a physical abacus, or in your head.

  1. 1
    1
    + 8
    + 3
    ?
  2. 2
    8
    + 5
    + 1
    ?
  3. 3
    4
    − 2
    + 5
    ?
  4. 4
    2
    + 7
    − 3
    ?
  5. 5
    1
    + 8
    + 6
    ?
  6. 6
    2
    + 8
    + 3
    ?
  7. 7
    8
    + 7
    − 6
    ?
  8. 8
    5
    − 2
    − 3
    ?
  9. 9
    5
    + 6
    + 2
    ?
  10. 10
    4
    + 7
    + 2
    ?
Full answer key
  1. 1 + 8 + 3 = 12
  2. 8 + 5 + 1 = 14
  3. 4 − 2 + 5 = 7
  4. 2 + 7 − 3 = 6
  5. 1 + 8 + 6 = 15
  6. 2 + 8 + 3 = 13
  7. 8 + 7 − 6 = 9
  8. 5 − 2 − 3 = 0
  9. 5 + 6 + 2 = 13
  10. 4 + 7 + 2 = 13

This page is one drill. The app is the whole programme.

Kani Math is a full mental-arithmetic course, not a single exercise. Free to start, no signup, and it runs on the web, Android and iPhone.

  • ✓Nine levels, from the first bead to division
  • ✓Guided lessons that teach the technique, not just drills
  • ✓Flash, listening and abacus drills at a speed you set
  • ✓Versus matches against friends or the computer
  • ✓Say your answers out loud — the app listens and marks them
  • ✓Streaks, coins and badges, with parent and teacher views

Want to stay here? The demo further down runs right on this page.

Launch App →Try the demo ↓

Practise it now

The same drill, live in your browser, with a virtual soroban and instant marking.

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Loads a full interactive drill right here on the page. It never asks who you are.

No signup. Nothing saved unless you ask.

Explore the free virtual abacus →How to use an abacus →Mental Math Drill →

About this drill

This is the stage where the soroban stops being a toy and starts being a calculator. Each problem stacks three single digits; the child works down the column, moving beads for each row in turn, and reads the answer off the rod at the end. Nothing is written down and nothing is held in memory — the abacus is the memory.

Every problem here is solvable with direct moves. If a row needs a bead that is not free, that is a complement problem and it belongs to the 5-complement and 10-complement pages, not this one. Getting fluent on direct moves first is what makes the complement rules feel like a shortcut later rather than a new subject.

How to practise it

  1. 1Read the whole column before touching a bead.
  2. 2Work top to bottom; never skip a row to "make it easier".
  3. 3Use thumb for earth beads up, index for everything else.
  4. 4Read the answer off the rod — do not recompute it in your head.
Where this sits

Level 2 — Basic

1-digit addition and subtraction on the soroban.

Teaches: 1-digit addition and subtraction

Find your level with the free placement exam →

Questions

Why three rows instead of two?
Two rows can be done by recall — most children already know 3 + 4. Three rows forces the abacus to carry the running total, which is the actual skill.
Can the answer go negative?
Not in these drills. A soroban has no sign, so every running total stays at zero or above. Negative work comes much later and uses a different technique.
My child guesses the answer instead of using beads.
Common, and worth correcting now. Cover the answer, slow the pace right down, and insist the beads move for every row even when the sum is obvious.
What comes after this?
Small friends — the 5-complement rules — which handle the cases where the bead you need is not free.
Learn the techniqueSmall friends (5-complements)Walk through it on the beads →