'One fifth' in the Bible

Let Pharaoh take action to appoint overseers and officials over the land, and set aside one-fifth [of the produce] of the [entire] land of Egypt in the seven years of abundance.

At harvest time [when you reap the increase] you shall give one-fifth of it to Pharaoh, and four-fifths will be your own to use for seed for the field and as food for you and those of your households and for your little ones.”

or anything about which he has sworn falsely; he shall not only restore it in full, but shall add to it one-fifth more. He shall give it to the one to whom it belongs on the day of his guilt offering.

But if a person unknowingly eats a holy gift [which has been offered to God], then he shall add one-fifth of its value to it and give the holy gift to the priest.

For the entrance of the Holy of Holies he made two [folding] doors of olive wood, the lintel (header above the door) and five-sided doorposts (frames).