Math

QuestionSuppose AA and BB are independent events. If P(A)=0.4P(A)=0.4 and P(B)=0.9P(B)=0.9, what is P(AB)P\left(A^{\prime} \cap B\right) ? A. 0.04 B. 0.36 C. 0.06 D. 0.54

Studdy Solution

STEP 1

What is this asking? If two events are independent, and we know how likely each one is to happen, how likely is it that the first one *doesn't* happen and the second one *does*? Watch out! Don't forget what "independent events" means, and don't mix up intersection and union!

STEP 2

1. Define Independence
2. Calculate the Probability of A'
3. Calculate the Probability of A' intersect B
4. Find the Answer

STEP 3

Alright, so, *independent events* mean that one event happening doesn't change the chance of the other event happening.
Think of flipping a coin and rolling a die – they don't affect each other!

STEP 4

AA' is the *complement* of AA, meaning it's everything *except* AA.
Since the total probability is always **1**, the probability of AA' is 11 minus the probability of AA.
So, P(A)=1P(A)P(A') = 1 - P(A).

STEP 5

We know that P(A)=0.4P(A) = \mathbf{0.4}, so P(A)=10.4=0.6P(A') = 1 - \mathbf{0.4} = \mathbf{0.6}.
Awesome!

STEP 6

Now, we need to find P(AB)P(A' \cap B), which means the probability of *both* AA' and BB happening.
Since AA and BB are independent, so are AA' and BB.
This means we can just multiply their probabilities!

STEP 7

So, P(AB)=P(A)P(B)P(A' \cap B) = P(A') \cdot P(B).
We just found P(A)=0.6P(A') = \mathbf{0.6} and we know P(B)=0.9P(B) = \mathbf{0.9}.

STEP 8

Let's multiply! P(AB)=0.60.9=0.54P(A' \cap B) = \mathbf{0.6} \cdot \mathbf{0.9} = \mathbf{0.54}.

STEP 9

We've got our final answer: P(AB)=0.54P(A' \cap B) = \mathbf{0.54}.
Which matches answer choice **D**!

STEP 10

The probability P(AB)P(A' \cap B) is **0.54**, so the correct answer is **D**.

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