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Use the data in the following table, which lists drive-thru order accuracy at popular fast food chains. Assume that orders are randomly selected from those included in the table.

\begin{tabular}{|l|c|c|c|c|}
\hline & A & B & C & D \\
\hline Order Accurate & 322 & 280 & 243 & 140 \\
\hline Order Not Accurate & 35 & 52 & 38 & 17 \\
\hline
\end{tabular}

If one order is selected, find the probability of getting an order from Restaurant A or an order that is accurate. Are the events of selecting an order from Restaurant A and selecting an accurate order disjoint events?

The probability of getting an order from Restaurant A or an order that is accurate is [tex]$\square$[/tex].
(Round to three decimal places as needed.)

Sagot :

Let's break down the problem step by step.

### Step 1: Calculate the total number of orders for each restaurant

From the given data:

- Restaurant A: 322 accurate + 35 not accurate = 357 total orders
- Restaurant B: 280 accurate + 52 not accurate = 332 total orders
- Restaurant C: 243 accurate + 38 not accurate = 281 total orders
- Restaurant D: 140 accurate + 17 not accurate = 157 total orders

### Step 2: Calculate the total number of orders

Adding up the total orders from all restaurants:
[tex]\[ 357 + 332 + 281 + 157 = 1127 \][/tex]
There are 1127 total orders.

### Step 3: Calculate the probabilities

#### 3.1 Probability of getting an order from Restaurant A
[tex]\[ \text{Probability of A} = \frac{\text{Total orders from A}}{\text{Total orders}} = \frac{357}{1127} \approx 0.317 \][/tex]

#### 3.2 Probability of getting an accurate order
Adding up the accurate orders from all restaurants:
[tex]\[ 322 + 280 + 243 + 140 = 985 \][/tex]
[tex]\[ \text{Probability of accurate order} = \frac{\text{Total accurate orders}}{\text{Total orders}} = \frac{985}{1127} \approx 0.874 \][/tex]

#### 3.3 Probability of getting an accurate order from Restaurant A
[tex]\[ \text{Probability of accurate order from A} = \frac{\text{Accurate orders from A}}{\text{Total orders}} = \frac{322}{1127} \approx 0.286 \][/tex]

### Step 4: Calculate the probability of getting an order from Restaurant A or an order that is accurate

Using the formula [tex]\( P(A \text{ or } B) = P(A) + P(B) - P(A \text{ and } B) \)[/tex]:
[tex]\[ P(A \text{ or Accurate}) = P(A) + P(\text{Accurate}) - P(A \text{ and Accurate}) \][/tex]
[tex]\[ P(A \text{ or Accurate}) = 0.317 + 0.874 - 0.286 = 0.905 \][/tex]

So, the probability of getting an order from Restaurant A or an order that is accurate is:
[tex]\[ \boxed{0.905} \][/tex]

### Step 5: Check if the events are disjoint

Two events are disjoint if they cannot occur simultaneously. Here, selecting an order from Restaurant A and selecting an accurate order can indeed occur at the same time, as seen from the probability calculation for accurate orders from A.

Therefore, the events of selecting an order from Restaurant A and selecting an accurate order are not disjoint.

### Summary:

- The probability of getting an order from Restaurant A or an order that is accurate is [tex]\( \boxed{0.905} \)[/tex].
- The events of selecting an order from Restaurant A and selecting an accurate order are not disjoint.