Minimum size of generating set of extension group is bounded by sum of minimum size of generating set of normal subgroup and quotient group

From Groupprops

This article gives the statement, and possibly proof, of a group property (i.e., finitely generated group) satisfying a group metaproperty (i.e., extension-closed group property)
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Statement

Quantitative version

Suppose is a group, is a normal subgroup, and is the corresponding quotient group. If denotes the minimum size of generating set for and denotes the minimum size of generating set for , then the minimum size of generating set for is at most .

Corollary for finitely generated groups

Suppose is a group, is a normal subgroup, and is the corresponding quotient group. Then, if both and are finitely generated groups, so is .

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