To begin, I am not currently in high school or college, this problem is one that was posed to me by a friend of mine trying to optimally play a video game where there is a bank of 27 skills, and each time you level up you get one choice out of 4 random skills, for 8 levels. That friend wants to know the chance of getting any specific skill in a run.
I will word the problem as follows:
you have 27 cards, labeled 1-27, face down in a deck and shuffled.
you pick 4 completely random cards from the deck, and look at them. if one of the cards is #1, keep it, and put the other 3 back in the deck and shuffle it.
if one of those cards is NOT #1, pick a random card from the 4 you drew, and put the remaining 3 back in the deck and shuffle it.
repeat this process 7 more times, until you have 8 cards in your hand and 19 in the deck.
what is the probability that one of the 8 cards is the #1 card?
to be clear: one of the 4 cards in your first pick could be the #1 card, making the remaining 7 draws just random cards.
there is also a chance that you will not get the #1 card at all.
I will word the problem as follows:
you have 27 cards, labeled 1-27, face down in a deck and shuffled.
you pick 4 completely random cards from the deck, and look at them. if one of the cards is #1, keep it, and put the other 3 back in the deck and shuffle it.
if one of those cards is NOT #1, pick a random card from the 4 you drew, and put the remaining 3 back in the deck and shuffle it.
repeat this process 7 more times, until you have 8 cards in your hand and 19 in the deck.
what is the probability that one of the 8 cards is the #1 card?
to be clear: one of the 4 cards in your first pick could be the #1 card, making the remaining 7 draws just random cards.
there is also a chance that you will not get the #1 card at all.