The word(s) "sixth" appears 5 time(s) in 4 verse(s) in Quran in Mohsin Khan translation.

(1) Allah commands you as regards your children's (inheritance): to the male, a portion equal to that of two females; if (there are) only daughters, two or more, their share is two-thirds of the inheritance; if only one, her share is a half. For parents, a sixth share of inheritance to each if the deceased left children; if no children, and the parents are the (only) heirs, the mother has a third; if the deceased left brothers (or sisters), the mother has a sixth. (The distribution in all cases is) after the payment of legacies he may have bequeathed or debts. You know not which of them, whether your parents or your children, are nearest to you in benefit; (these fixed shares) are ordained by Allah. And Allah is Ever All-Knower, All-Wise.

(2) In that which your wives leave, your share is a half if they have no child; but if they leave a child, you get a fourth of that which they leave after payment of legacies that they may have bequeathed or debts. In that which you leave, their (your wives) share is a fourth if you leave no child; but if you leave a child, they get an eighth of that which you leave after payment of legacies that you may have bequeathed or debts. If the man or woman whose inheritance is in question has left neither ascendants nor descendants, but has left a brother or a sister, each one of the two gets a sixth; but if more than two, they share in a third, after payment of legacies he (or she) may have bequeathed or debts, so that no loss is caused (to anyone). This is a Commandment from Allah; and Allah is Ever All-Knowing, Most-Forbearing.

(3) (Some) say they were three, the dog being the fourth among them; and (others) say they were five, the dog being the sixth, - guessing at the unseen; (yet others) say they were seven, and the dog being the eighth. Say (O Muhammad صلى الله عليه وسلم): "My Lord knows best their number; none knows them but a few." So debate not (about their number) except with the clear proof (which We have revealed to you). And consult not any of them (people of the Scripture - Jews and Christians) about (the affair of) the people of the Cave.

(4) Have you not seen that Allah knows whatsoever is in the heavens and whatsoever is on the earth? There is no Najwa (secret counsel) of three but He is their fourth (with His Knowledge, while He Himself is over the Throne, over the seventh heaven), nor of five but He is their sixth (with His Knowledge), nor of less than that or more but He is with them (with His Knowledge) wheresoever they may be. And afterwards on the Day of Resurrection He will inform them of what they did. Verily, Allah is the All-Knower of everything.