Who knows a fifth?
?חמישית - מי יודע
In the spirit of the song "Echad - mi yodeya", please post interesting and significant Jewish facts about the number 0.2.
Lazy gematria may be worthy of discission, but perhaps not of a full-fledged answer. [This may not apply in the conventional sense, but, e.g., saying x is a quarter of y is just not keeping in the spirit. However, there maybe be examples that the Arizal, Baal Haturim, etc., mention and they are perfect for comments.]
Check out mi-yodeya-series for the previous three hundred fifty entries in this ongoing series.
Please include sources for your information wherever possible, as with all other answers on this site.