contestada

7. A card is drawn from a standard deck, not
replaced and another is drawn. What is the
probability of choosing a heart then a spade?

Respuesta :

Answer:

probability = [tex]\displaystyle\bf\frac{13}{204}[/tex]

Step-by-step explanation:

We can find the probability of choosing a heart then a spade without replacement by using the probability formula:

[tex]\boxed{P(A)=\frac{n(A)}{n(S)} }[/tex]

where:

  • [tex]P(A)[/tex] = probability of event A
  • [tex]n(A)[/tex] = total outcomes of event A
  • [tex]n(S)[/tex] = total outcomes of all possibilities

Let:

  • A = drawing a heart at the 1st draw
  • B|A = drawing a spade after the event A

For the 1st draw:

  • total number of hearts [tex](n(A))[/tex] = 13
  • total number of cards [tex](n(S)_A)[/tex] = 52

[tex]\displaystyle P(A)=\frac{n(A)}{n(S)_A}[/tex]

        [tex]\displaystyle=\frac{13}{52}[/tex]

        [tex]\displaystyle=\frac{1}{4}[/tex]

For the 2nd draw:

  • total number of spade [tex](n(B|A))[/tex] = 13
  • total number of cards [tex](n(S)_B)[/tex] = 52 - 1 = 51 (1 card is taken without replacement at the 1st draw)

[tex]\displaystyle P(B|A)=\frac{n(B|A)}{n(S)_B}[/tex]

            [tex]\displaystyle=\frac{13}{51}[/tex]

            [tex]\displaystyle=\frac{1}{4}[/tex]

Hence, for the event "drawing a heart at the 1st draw" AND "drawing a spade after the event A":

[tex]P(A\cup B)=P(A)\times P(B|A)[/tex]

               [tex]\displaystyle=\frac{1}{4} \times\frac{13}{51}[/tex]

               [tex]\displaystyle=\bf\frac{13}{204}[/tex]

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