Kani Math
Cosmic Abacus
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Abacus flash cards

Numbers appear one at a time and vanish. Nothing stays on screen, so nothing can be re-read — the total lives in your head or nowhere.

  • 4 rows × 2 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
    71
    + 28
    + 69
    + 50
    ?
  2. 2
    76
    − 72
    + 64
    + 39
    ?
  3. 3
    10
    + 81
    + 89
    + 13
    ?
  4. 4
    81
    + 47
    − 21
    + 93
    ?
  5. 5
    12
    + 66
    + 18
    + 16
    ?
  6. 6
    37
    + 78
    + 27
    + 17
    ?
  7. 7
    17
    + 94
    + 34
    + 70
    ?
  8. 8
    36
    + 76
    + 10
    − 32
    ?
  9. 9
    16
    + 85
    + 45
    − 66
    ?
  10. 10
    88
    − 51
    − 29
    + 34
    ?
Full answer key
  1. 71 + 28 + 69 + 50 = 218
  2. 76 − 72 + 64 + 39 = 107
  3. 10 + 81 + 89 + 13 = 193
  4. 81 + 47 − 21 + 93 = 200
  5. 12 + 66 + 18 + 16 = 112
  6. 37 + 78 + 27 + 17 = 159
  7. 17 + 94 + 34 + 70 = 215
  8. 36 + 76 + 10 − 32 = 90
  9. 16 + 85 + 45 − 66 = 80
  10. 88 − 51 − 29 + 34 = 42

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.

It also delivers the numbers for you — flashed on screen or read aloud, with the speed, digit count and number of rows under your control. That is the one thing a printed page cannot do.

  • ✓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

A printed column can be re-read. A flash card cannot. That single difference changes what is being trained: with a column, a learner can recover from a lapse by glancing back; with flashed numbers, a lapse ends the problem. The exercise stops being about arithmetic and becomes about maintaining a value under time pressure.

Flash cards are also the cleanest way to break a learner off finger counting and written intermediates, because neither is fast enough to keep up. Start slow — two seconds per number is plenty — and shorten the interval only when accuracy holds.

How to practise it

  1. 1Set the interval slow enough that accuracy stays at 100%.
  2. 2Look at the centre of the screen, not at each number.
  3. 3Update the running total on every flash; never let one pass unprocessed.
  4. 4Shorten the interval by a fraction only after a clean full set.

Questions

What is the difference between flash cards and flash anzan?
Flash cards are the format; flash anzan is flash cards worked on a mentally visualized abacus. You can use flash cards with beads in front of you, and many learners do at first.
What interval should we start at?
Two seconds per number. Anything faster while accuracy is still settling just trains guessing.
My child does well on paper but badly here.
That is the normal pattern, and it means paper work was leaning on re-reading. A few weeks of flash practice usually closes it.
Are these the same as multiplication flash cards?
No. Standard flash cards test recall of a single fact. These test maintaining a running total across several numbers, which is a different skill.
Learn the techniqueMental abacus (anzan)Walk through it on the beads →