Mental Math

Drills at a digit count and operation set you pick, and division always comes out even.

equations.arithmetic · v1 · renderer math

1. 70 + 96 → 166 2. 190/2 → 95 3. 531/9 → 59 4. 86 + 89 → 175 5. 40 - 19 → 21 6. 90 - 70 → 20 7. 97 + 98 → 195 8. 595/7 → 85 9. 90 - 67 → 23 10. 98*3 → 294

Controls · from schema()

Operations

Digits

1 4

How large the operands get.

How many

1 100

Allow negatives

Lets a subtraction go below zero, and operands turn negative.

Entropy source

Picking a source changes the story on the receipt, never the quality: anything below class A is mixed with the OS CSPRNG before it reaches you. This result actually came from ISS Position.

seed token GHN112CPDJMG9CKMYK144JRMXR

Re-render keeps this token. Generate replaces it. That is the whole idea.

Printable worksheet 20 problems · answers on page 2

The seed is printed in the footer, so the same sheet comes back from the same link — and a different seed is a different sheet.

entropy in

16 bytes

stream used

36 bytes

rejections

duration

390 µs

problems

Seed receipt

Class C · Observational

The ISS was over 14.61° N, 1.64° W — 1,010 km north of Accra — when this was drawn.

Carries only tens of bits of genuine surprise. Always mixed with the OS CSPRNG.

source: ISS Position
observed: 2026-10-28T22:11:00+00:00
latency: 158ms
mixed with: csprng — always

https://www.openstreetmap.org/#map=3/14.61/-1.64 ↗

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The token is the seed, so this link recomputes the result rather than looking it up. No database, and it works for as long as v1 does.

This page and /api/v1/g/equations.arithmetic run the same code. There is no private endpoint.

Mental Math

Result

Measurements

Seed receipt

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