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—statistics and probability, rules of probability

Question:
Mary has 10 blouses hanging in her closet— 5 are blue, 2 are black, and the rest are red. if she hangs the blouse in a random order, what is the probability that the first and last blouse are both red?

A. 0.011
B. 0.067
C. 0.042
D. 0.001


1 Answer

3 votes

Answer:

B. 0.067

Explanation:

A probability is the number of desired outcomes divided by the number of total outcomes.

Number of arrangements:

The number of possible arrangements of n elements is given by:


A_(n) = n!

Desired outcomes

First red(10 - (5+2) = 3 possible)

Last red(2 possible).

Middle 8 arranged in any way.

So


D = 3*A_(8)*2 = 3*8!*2 = 241920

Total outcomes:

Arrangements of 10 elements. So


T = A_(10) = 10! = 3628800

What is the probability that the first and last blouse are both red?


p = (D)/(T) = (241920)/(3628800) = 0.067

The correct answer is given by option B.

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