Kani Math
Cosmic Abacus
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Two-digit addition drills

Two rods, five rows, and carries that have to happen the moment they occur — the width where abacus method starts beating pencil and paper.

  • 5 rows × 2 digits, addition
  • About 7 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
    89
    + 95
    + 11
    + 22
    + 62
    ?
  2. 2
    89
    + 82
    + 85
    + 16
    + 19
    ?
  3. 3
    33
    + 77
    + 73
    + 98
    + 37
    ?
  4. 4
    54
    + 42
    + 59
    + 12
    + 76
    ?
  5. 5
    46
    + 32
    + 56
    + 18
    + 51
    ?
  6. 6
    54
    + 28
    + 62
    + 17
    + 40
    ?
  7. 7
    33
    + 58
    + 27
    + 32
    + 25
    ?
  8. 8
    96
    + 12
    + 30
    + 60
    + 63
    ?
  9. 9
    55
    + 16
    + 54
    + 93
    + 62
    ?
  10. 10
    37
    + 80
    + 12
    + 95
    + 69
    ?
Full answer key
  1. 89 + 95 + 11 + 22 + 62 = 279
  2. 89 + 82 + 85 + 16 + 19 = 291
  3. 33 + 77 + 73 + 98 + 37 = 318
  4. 54 + 42 + 59 + 12 + 76 = 243
  5. 46 + 32 + 56 + 18 + 51 = 203
  6. 54 + 28 + 62 + 17 + 40 = 201
  7. 33 + 58 + 27 + 32 + 25 = 175
  8. 96 + 12 + 30 + 60 + 63 = 261
  9. 55 + 16 + 54 + 93 + 62 = 280
  10. 37 + 80 + 12 + 95 + 69 = 293

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
  • ✓Four timed sprints and two practice exams, with leaderboards
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  • ✓Say your answers out loud — the app listens and marks them
  • ✓Streaks, coins and badges, a teacher view, and a parent dashboard with Premium
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Practise it now

A live drill of the same shape, 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.

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

About this drill

Two-digit columns are the first width where the written algorithm and the abacus genuinely diverge. On paper you add all the units, write a carry, then add all the tens. On the abacus the carry happens the instant it is created, so there is never a pending digit anywhere — which is exactly why the procedure survives being moved into the head later.

The drills below hold every running total under 500, so three rods are always enough and no problem needs a fourth. That constraint keeps the exercise about the carry itself rather than about managing a wider workspace.

How to practise it

  1. 1Set the first number on the two rightmost rods.
  2. 2Add each row tens first, then units, and make each carry on the rod to the left as it happens.
  3. 3Resolve every carry immediately; do not defer it to the end.
  4. 4Read all the rods together as one number when you finish; the carries can reach a third rod.

Questions

Why tens before units?
Because that is how the number is read and how mental calculation runs: the highest place first, so the total is roughly right from the first move. A carry from the units is one bead added on the tens rod at once, so nothing is left pending.
Do I need a real abacus?
No. The interactive drill on this page runs a full virtual soroban in the browser, and every sample below is solvable with pencil and paper too.
Is this the same as "2 digit abacus practice"?
Yes — two-digit here means each number in the column has two digits, so the work happens across two rods.
My child is accurate but slow.
That is the correct order. Speed comes from removing hesitation, not from hurrying; keep accuracy at 100% and let the pace rise on its own.
Learn the techniqueBig friends (10-complements)Walk through it on the beads →