Questions: A weighted number cube has faces labeled 1 through 6. Let X be the number shown on the cube when it is rolled. Here is the probability distribution of X.
Value x of X: 1, 2, 3, 4, 5, 6
P(X=x): 0.18, 0.28, 0.16, 0.15, 0.12, 0.11
For parts (a) and (b) below, find the probability that the number described is shown on a random roll.
(a) Greater than or equal to 5:
(b) Lower than 3:
Transcript text: A weighted number cube has faces labeled 1 through 6 . Let $X$ be the number shown on the cube when it is rolled. Here is the probability distribution of $X$.
\begin{tabular}{|c|c|c|c|c|c|c|}
\hline Value $\boldsymbol{x}$ of $\boldsymbol{X}$ & 1 & 2 & 3 & 4 & 5 & 6 \\
\hline $\boldsymbol{P}(\mathbf{X}=\boldsymbol{x})$ & 0.18 & 0.28 & 0.16 & 0.15 & 0.12 & 0.11 \\
\hline
\end{tabular}
For parts (a) and (b) below, find the probability that the number described is shown on a random roll.
(a) Greater than or equal to 5: $\square$
(b) Lower than 3: $\square$
Solution
Solution Steps
Step 1: Identify the probabilities for values greater than or equal to 5
From the probability distribution table:
\( P(X = 5) = 0.12 \)
\( P(X = 6) = 0.11 \)
Step 2: Calculate the probability for part (a)
The probability that \( X \) is greater than or equal to 5 is the sum of the probabilities for \( X = 5 \) and \( X = 6 \):
\[
P(X \geq 5) = P(X = 5) + P(X = 6) = 0.12 + 0.11 = 0.23
\]
Step 3: Identify the probabilities for values lower than 3
From the probability distribution table:
\( P(X = 1) = 0.18 \)
\( P(X = 2) = 0.28 \)
Step 4: Calculate the probability for part (b)
The probability that \( X \) is lower than 3 is the sum of the probabilities for \( X = 1 \) and \( X = 2 \):
\[
P(X < 3) = P(X = 1) + P(X = 2) = 0.18 + 0.28 = 0.46
\]