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The probability of drawing two white balls from a jar at random without replacement is [tex]\frac{1}{5}[/tex].

The probability of drawing a white ball first is [tex]\frac{7}{15}[/tex].

What is the probability of drawing a second white ball, given that the first ball drawn was white?

A. [tex]\frac{2}{3}[/tex]
B. [tex]\frac{7}{75}[/tex]
C. [tex]\frac{3}{7}[/tex]
D. [tex]\frac{4}{15}[/tex]


Sagot :

To find the probability of drawing a second white ball given that the first ball drawn was white, we will use conditional probability. This problem can be framed as finding [tex]\( P(B|A) \)[/tex], where:

- [tex]\( A \)[/tex] is the event of drawing a white ball first.
- [tex]\( B \)[/tex] is the event of drawing a white ball second.

We need to find [tex]\( P(B|A) \)[/tex], which is the conditional probability of [tex]\( B \)[/tex] given [tex]\( A \)[/tex]. According to the formula for conditional probability:

[tex]\[ P(B|A) = \frac{P(A \text{ and } B)}{P(A)} \][/tex]

We have the following information provided in the problem:

- [tex]\( P(A \text{ and } B) = \frac{1}{5} \)[/tex] (the probability of drawing two white balls consecutively).
- [tex]\( P(A) = \frac{7}{15} \)[/tex] (the probability of drawing a white ball first).

Now, substituting these values into the formula for conditional probability:

[tex]\[ P(B|A) = \frac{\frac{1}{5}}{\frac{7}{15}} \][/tex]

This simplifies to:

[tex]\[ P(B|A) = \frac{1/5}{7/15} = \frac{1/5 \times 15/7}{1} = \frac{15}{35} = \frac{3}{7} \][/tex]

Hence, the probability of drawing a second white ball given that the first ball drawn was white is [tex]\(\frac{3}{7}\)[/tex].

Therefore, the correct answer is [tex]\(\frac{3}{7}\)[/tex].