In traveling from city A to city B, John drove for 1 hour of 50 mph and for 3 hours at 60 mph. What was his average speed for the whole trip?

Options

A. 50
B. `53 1//2`
C. `55`
D. `57.5`

Answer

To find John's average speed for the whole trip from city A to city B, we will follow these steps:

### Step 1: Calculate the distance for the first part of the trip
John drove for 1 hour at a speed of 50 mph.
Using the formula for distance:
\[ \text{Distance} = \text{Speed} \times \text{Time} \]
For the first part:
\[ d_1 = 50 \, \text{mph} \times 1 \, \text{hour} = 50 \, \text{miles} \]

### Step 2: Calculate the distance for the second part of the trip
John drove for 3 hours at a speed of 60 mph.
Using the same formula for distance:
\[ d_2 = 60 \, \text{mph} \times 3 \, \text{hours} = 180 \, \text{miles} \]

### Step 3: Calculate the total distance traveled
Now, we can find the total distance by adding the distances from both parts of the trip:
\[ \text{Total Distance} = d_1 + d_2 = 50 \, \text{miles} + 180 \, \text{miles} = 230 \, \text{miles} \]

### Step 4: Calculate the total time taken
The total time taken for the trip is the sum of the time for both parts:
\[ \text{Total Time} = 1 \, \text{hour} + 3 \, \text{hours} = 4 \, \text{hours} \]

### Step 5: Calculate the average speed
Now we can calculate the average speed using the formula:
\[ \text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}} \]
Substituting the values we found:
\[ \text{Average Speed} = \frac{230 \, \text{miles}}{4 \, \text{hours}} = 57.5 \, \text{mph} \]

### Final Answer
John's average speed for the whole trip is **57.5 mph**.

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