# rule of sum

> counting principle in combinatorics

**Wikidata**: [Q2360148](https://www.wikidata.org/wiki/Q2360148)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Addition_principle)  
**Source**: https://4ort.xyz/entity/rule-of-sum


## References

1. Freebase Data Dumps. 2013
2. PlanetMath