インド式計算道Way of Indian Math
Way of Indian Math, editors№ 001

インド式計算道

Way of Indian Math

99 × 99 in seconds.

Thirteen methods. One mental-math practice.

From Level 1 to Master 7, each rank teaches a different way to see a multiplication. No ads, no network, just ink-quiet focus.

Knock at the dōjōAvailable on the App Store and Google Play
three, two, one—
№ Inaugural issue99×99= 9801

Editorial dispatch

Why five seconds is enough.

Indian-style mental math is not a shortcut. You split the place values, find a symmetry, and rewrite the expression as something simpler. The long form disappears.

Worked example: 37 × 43

  1. 01

    37 × 43

    Long multiplication takes four lines.

  2. 02

    = (40 − 3)(40 + 3)

    Average is 40, the gap is 3.

  3. 03

    = 40² − 3²

    Sum × difference is a difference of squares.

  4. 04

    = 1600 − 9

    Squares are well within recall.

  5. 05

    = 1591

    Done. Four seconds.

Each of the thirteen methods spots a different symmetry.

Curriculum

Thirteen ways of seeing.

Each method is the shortest path through one specific pattern. You don't memorise it — you learn to see it.

Rank

Pattern

Example

  1. 01 / 級Level 1
    ab × 11Multiplying by 11
    26 × 11 = 286
  2. 02 / 級Level 2
    (ab) × (cb), a+c=10Same ones, tens sum to 10
    35 × 75 = 2625
  3. 03 / 級Level 3
    (ab) × (ac), b+c=10Same tens, ones sum to 10
    43 × 47 = 2021
  4. 04 / 級Level 4
    (1a) × (1b)Both numbers in 11–19
    13 × 14 = 182
  5. 05 / 級Level 5
    (N − d)(N + d)Average is a round number
    37 × 43 = 1591
  6. 06 / 級Level 6
    Numbers near 100Both numbers in the 90s
    97 × 96 = 9312
  7. 07 / 段Master 1
    2-digit × 1-digit2-digit × 1-digit
    37 × 6 = 222
  8. 08 / 段Master 2
    even × ones-is-5Even 2-digit × ones-is-5
    24 × 35 = 840
  9. 09 / 段Master 3
    (a5) × (b5)Both end in 5
    35 × 75 = 2625
  10. 10 / 段Master 4
    even × 25 / 75Even 2-digit × 25 / 75
    68 × 25 = 1700
  11. 11 / 段Master 5
    (a1) × (b1)Both end in 1
    31 × 41 = 1271
  12. 12 / 段Master 6
    (ab) × (ac), same tensSame tens digit
    34 × 37 = 1258
  13. 13 / 段Master 7
    Vertical & crosswiseGeneral 2-digit × 2-digit
    47 × 58 = 2726

Ranked path

Thirteen seals, Level 1 to Master 7.

Five seconds per question, fifty for the round of twenty. Mistakes cost time. That's the price of a seal.

  1. 01Level 1

    Multiplying by 11

  2. 02Level 2

    Same ones, tens sum to 10

  3. 03Level 3

    Same tens, ones sum to 10

  4. 04Level 4

    Both numbers in 11–19

  5. 05Level 5

    Average is a round number

  6. 06Level 6

    Both numbers in the 90s

  7. 07Master 1

    2-digit × 1-digit

  8. 08Master 2

    Even 2-digit × ones-is-5

  9. 09Master 3

    Both end in 5

  10. 10Master 4

    Even 2-digit × 25 / 75

  11. 11Master 5

    Both end in 1

  12. 12Master 6

    Same tens digit

  13. 13Master 7

    General 2-digit × 2-digit

From the pages

What's inside.

2級 / Master3 / 20

37 × 43

= ?

1591

残り 1.9s

Question screen

Just the time and the expression. The rest is space for thinking.

MASTER COURSE

修行の地図

  1. ✓6級
  2. ✓5級
  3. ✓4級
  4. ▶3級
  5. ·2級
  6. ·1級
  7. ·初段
  8. ·二段
  9. ·三段
  10. ·四段
  11. ·五段
  12. ·六段
  13. ·七段

The path

Thirteen ranks at a glance. Seals stack as you climb.

合格

ぴったり 47.6秒

1問あたり 平均 2.4s

Pass screen

Confetti and Ganesha's blessing.

Price

¥350. Once.

One-time. No ads. No subscriptions. No accounts.

One-time

¥350

(tax incl.)

買い切り⁝ ⁝ ⁝

01 / 4

Zero ads

No ad SDK, no interruption to learning.

02 / 4

Fully offline

The app holds no network permission.

03 / 4

Five languages

Japanese, English, Korean, Chinese, French.

04 / 4

iOS / Android

Both platforms covered for ¥350.

Frequently asked

What you might be wondering.

  • 01Is it really one-time?

    Yes. ¥350 unlocks all thirteen methods and all thirteen ranks. No subscriptions, no in-app purchases.

  • 02Is it suitable for children?

    Yes, from upper elementary age. The expressions are number-led, designed to work with a parent alongside.

  • 03Does it work offline?

    Yes. The app holds no network permission. All progress and best times stay on the device.

  • 04Are there ads?

    No. No ad SDK is included.

  • 05Do I need an account?

    No. There is no account system, no cloud sync. History does not transfer between devices.

  • 06Which languages are supported?

    Japanese, English, Korean, Chinese (Simplified), and French. The app follows your OS language.

  • 07Why five seconds per question?

    Five seconds is a sane upper bound for the three steps of mental math: read, see the pattern, build the answer aloud. Beyond that, you're doing long multiplication.