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End of Course Test

Jim decides to start a small nonprofit business renting out motor scooters to help his area residents. He invests his own money and buys 5 motor scooters, each priced at [tex]$\$[/tex] 3,000[tex]$. He incurs no other costs because he keeps the motor scooters in his own garage. The motor scooters last for 5 years. The number of motor scooters and the probability that they will be rented per month is shown in the table below.

\begin{tabular}{|c|c|c|c|c|c|c|}
\hline Number of Scooters & 0 & 1 & 2 & 3 & 4 & 5 \\
\hline Probability & $[/tex]\frac{1}{32}[tex]$ & $[/tex]\frac{5}{32}[tex]$ & $[/tex]\frac{10}{32}[tex]$ & $[/tex]\frac{10}{32}[tex]$ & $[/tex]\frac{5}{32}[tex]$ & $[/tex]\frac{1}{32}$ \\
\hline
\end{tabular}

Using this distribution, what is the expected number of motor scooters to be rented out in a month?

A. 1

B. 1.5

C. 2

D. 2.5

E. 3


Sagot :

To determine the expected number of motor scooters rented out in a month, we need to calculate the expected value (mean) using the given probabilities for each possible number of rented scooters.

The formula for the expected value [tex]\( E(X) \)[/tex] where [tex]\( X \)[/tex] is a discrete random variable is:
[tex]\[ E(X) = \sum_{i=1}^{n} x_i \cdot P(x_i) \][/tex]

Here, [tex]\( x_i \)[/tex] is each possible value of [tex]\( X \)[/tex] (in our case, the number of scooters), and [tex]\( P(x_i) \)[/tex] is the corresponding probability.

Given the data:
- Number of scooters ([tex]\( x_i \)[/tex]): 0, 1, 2, 3, 4, 5
- Probabilities ([tex]\( P(x_i) \)[/tex]): [tex]\( \frac{1}{32} \)[/tex], [tex]\( \frac{5}{32} \)[/tex], [tex]\( \frac{10}{32} \)[/tex], [tex]\( \frac{10}{32} \)[/tex], [tex]\( \frac{5}{32} \)[/tex], [tex]\( \frac{1}{32} \)[/tex]

Now, let's calculate the expected value step by step:

1. Multiply each number of scooters by its corresponding probability:
- [tex]\( 0 \cdot \frac{1}{32} = 0 \)[/tex]
- [tex]\( 1 \cdot \frac{5}{32} = \frac{5}{32} \)[/tex]
- [tex]\( 2 \cdot \frac{10}{32} = \frac{20}{32} \)[/tex]
- [tex]\( 3 \cdot \frac{10}{32} = \frac{30}{32} \)[/tex]
- [tex]\( 4 \cdot \frac{5}{32} = \frac{20}{32} \)[/tex]
- [tex]\( 5 \cdot \frac{1}{32} = \frac{5}{32} \)[/tex]

2. Sum these products:
[tex]\[ 0 + \frac{5}{32} + \frac{20}{32} + \frac{30}{32} + \frac{20}{32} + \frac{5}{32} = \frac{5 + 20 + 30 + 20 + 5}{32} = \frac{80}{32} = 2.5 \][/tex]

Thus, the expected number of motor scooters to be rented out in a month is [tex]\( 2.5 \)[/tex].

Therefore, the correct answer is:
[tex]\[ \boxed{2.5} \][/tex]