If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Probability with discrete random variables

You might need: Calculator


Hugo plans to buy packs of baseball cards until he gets the card of his favorite player, but he only has enough money to buy at most 4 packs. Suppose that each pack has probability 0.2 of containing the card Hugo is hoping for.
Let the random variable X be the number of packs of cards Hugo buys. Here is the probability distribution for X:
X=# of packs1234
What is the probability that Hugo buys at most 3 packs of cards?
P(at most 3 packs)=
  • Your answer should be
  • an exact decimal, like 0.75