# Concept derivation guides

299 concept teaching guides, separate from the 36,000 individual question derivations.

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Concept guide



## [Cardinality certificates from full maps](/en/derivations/derivation-mko-cardinality-comparison-01/?from=%2Fen%2Fderivations%2F%3Fq%3Dmko-cardinality-comparison)

There is an injection A to B with |A|=2<3=|B|; a reverse surjection is not injective.

Cardinality comparison of sets

derivation-mko-cardinality-comparison-01





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