# Modular Arithmetic Basics

Canonical: https://manyspace.aporia.systems/topics/modular-arithmetic-basics-mth-disc-121
Updated: 2026-10-13

Mathematics · Discrete Mathematics · MTH-DISC-121

- Difficulty: 3 / 5
- Importance: 4 / 5
- Study time: 4–7.5 h

congruence, clock arithmetic, divisibility rules

## Why it matters

The mathematics of discrete structures underlying computer science, combinatorics and modern applied math.

## Where it is used

Algorithms and data structures, networks, cryptography, probability counting, game design, scheduling.

## How you know you have learned it

Solve ≥10 representative problems with ≥80% adjusted accuracy.

## What you need first

- [Direct Proof](https://manyspace.aporia.systems/topics/direct-proof-mth-proofs-104) (required)

## Resources

- Discrete Mathematics and Its Applications (Rosen) — Kenneth Rosen
- Discrete Mathematics and Its Applications (Rosen) — Kenneth Rosen
- Concrete Mathematics — Graham, Knuth & Patashnik