Question

Two cards are drawn in succession from a standard 52-card deck.1. What is the probability that the first card is red and the second card is black(A) If the cards are drawn without replacement?(B) If the cards are drawn with replacement?2. Two balls are drawn in succession out of a box containing 3 red and 5 white balls. Find the probability that at least 1 ball was red, given that the first ball was(A) Replaced before the second draw(B) Not replaced before the second drawContext Header: Conditional ProbabilityContext Section:Conditional Probability is a calculation of the likelihood of an occurrence provided that another event has already occurred. Conditional probability A provided B is generally written as:P(A/B)=P(A∩B)P(B)

Answer 1

52 cards:

26 red and 26 black

P(R) = probability of picking a red card

P(B) = probability of picking a black card

P(R) = P(B) = ¹/₂

If with replacement:

P(R∩B) = (¹/₂)(¹/₂) = ¹/₄

If without replacement:

P(R∩B) = (¹/₂)(²⁶/₅₁) = ¹³/₅₁

8 Balls:

3 red and 5 white

P(R) = probability of picking a red ball

P(W) = probability of picking a white ball

P(R) = ³/₈

P(W) = ⁵/₈

If with replacement:

P(R∩W) ∪ P(W∩R) = (³/₈)(⁵/₈) + (⁵/₈)(³/₈)

= ¹⁵/₆₄ + ¹⁵/₆₄

= ³⁰/₆₄

= ¹⁵/₃₂

If without replacement:

P(R∩W) ∪ P(W∩R) = (³/₈)(⁵/₇) + (⁵/₈)(³/₇)

= ¹⁵/₄₂ + ¹⁵/₄₂

= ³⁰/₄₂

= ⁵/₇