A bag contains 5 red and 7 blue balls. Find the probability of drawing 2 red balls without replacement.
Show Hint
For probabilities without replacement:
- The total number of items decreases after each draw.
- Use conditional probability \(P(A \cap B) = P(A)P(B|A)\).
Concept:
For probability without replacement, the outcome of the first event affects the probability of the second event. The multiplication rule of probability is used:
\[
P(A \cap B) = P(A) \times P(B|A)
\]
Step 1: Total number of balls.
\[
5 \text{ red} + 7 \text{ blue} = 12 \text{ balls}
\]
Step 2: Probability of drawing the first red ball.
\[
P(\text{First Red}) = \frac{5}{12}
\]
Step 3: Probability of drawing the second red ball.
After drawing one red ball, \(4\) red balls remain out of \(11\) total balls.
\[
P(\text{Second Red}) = \frac{4}{11}
\]
Step 4: Calculate the total probability.
\[
P(\text{Two Reds}) =
\frac{5}{12} \times \frac{4}{11}
\]
\[
= \frac{20}{132} = \frac{5}{33}
\]
Thus, the required probability is:
\[
\boxed{\frac{5}{33}}
\]