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If three balls are drawn one by one without replacement from a bag containing 5 white and 4 red balls, then the probability distribution of the number of white balls drawn is

Solution

✅ Correct Option: 2

The bag contains 5 white balls and 4 red balls, for a total of 9 balls. Three balls are drawn one by one without replacement. X represents the number of white balls drawn.

The total number of ways to draw 3 balls from 9 balls:

C(9,3)=9!3!×6!C(9,3) = \dfrac{9!}{3! \times 6!}

=9×8×73×2×1= \dfrac{9 \times 8 \times 7}{3 \times 2 \times 1}

=5046= \dfrac{504}{6}

=84= 84


For X = 0 (no white balls, all 3 red):

Number of ways to choose 0 white from 5: C(5,0)=1C(5,0) = 1

Number of ways to choose 3 red from 4: C(4,3)=4C(4,3) = 4

Favorable outcomes =1×4=4= 1 \times 4 = 4

P(X=0)=484=121P(X = 0) = \dfrac{4}{84} = \dfrac{1}{21}


For X = 1 (exactly 1 white ball):

Number of ways to choose 1 white from 5: C(5,1)=5C(5,1) = 5

Number of ways to choose 2 red from 4: C(4,2)=6C(4,2) = 6

Favorable outcomes =5×6=30= 5 \times 6 = 30

P(X=1)=3084=514P(X = 1) = \dfrac{30}{84} = \dfrac{5}{14}


For X = 2 (exactly 2 white balls):

Number of ways to choose 2 white from 5: C(5,2)=10C(5,2) = 10

Number of ways to choose 1 red from 4: C(4,1)=4C(4,1) = 4

Favorable outcomes =10×4=40= 10 \times 4 = 40

P(X=2)=4084=1021P(X = 2) = \dfrac{40}{84} = \dfrac{10}{21}


For X = 3 (all 3 white balls):

Number of ways to choose 3 white from 5: C(5,3)=10C(5,3) = 10

Number of ways to choose 0 red from 4: C(4,0)=1C(4,0) = 1

Favorable outcomes =10×1=10= 10 \times 1 = 10

P(X=3)=1084=542P(X = 3) = \dfrac{10}{84} = \dfrac{5}{42}


The probability distribution is:

X0123
P(X)1/215/1410/215/42

Therefore, the answer is Option 2.

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