Question

Which probability rule would you use? Calculate the results.

You drew a 10 and then you drew a 6. You want to figure out the probability of getting to 20 or 21 with the next card.

Which probability rule would you use? Calculate the results.

You drew a 10 and then placed it back in the deck. You want to figure out the probability that you will draw a 6 or a 7 next.

With replacement

Which probability rule would you use? Calculate the results.
You want to figure out the probability that you will draw a 6, put the 6 back in the deck, and then draw a 7.
With replacement

Answer 1

a) The only way to get to 20 or 21 is if we drew a 4 or 5 from the deck of 50 cards (because we have already drawn a 10 and 6).

We will use the Addition Rule to obtain our result.

P(20 or 21) = P(4 or 5) = P(4) + P(5)

= 4/50 + 4/50

= 4/25

b) Now that we have replaced the card that was initially drawn. The deck has complete 52 cards.

We will again use the Addition Rule .

P(6 or 7) = P(6) + P(7) = 4/52 + 4/52

= 2/13

c) In this case drawing a 6 and drawing a 7 are independent events since we are replacing them back in the deck.

We will use the Multiplication Rule.

P(6 and 7) = P(6) * P(7)

= 4/52 * 4/52

= 1/169