MathDB
ratio wanted, paper folding a square (2019 Novosibirsk Oral Geo Oly 8.3)

Source:

April 28, 2021
ratiopaper foldingfoldinggeometrysquare

Problem Statement

A square sheet of paper ABCDABCD is folded straight in such a way that point BB hits to the midpoint of side CDCD. In what ratio does the fold line divide side BCBC?