A car covers 630 km in 20 hours. Calculate its average speed in meters/second ?

Options

A. 8.25
B. 7.75
C. 8.75
D. 7.25

Answer

To calculate the average speed of the car in meters per second, we can follow these steps:

### Step 1: Understand the given data
The car covers a distance of 630 km in a time of 20 hours.

### Step 2: Calculate the average speed in km/h
We can use the formula for speed:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \]
Substituting the values:
\[ \text{Speed} = \frac{630 \text{ km}}{20 \text{ hours}} \]
\[ \text{Speed} = 31.5 \text{ km/h} \]

### Step 3: Convert km/h to m/s
To convert the speed from kilometers per hour to meters per second, we can use the conversion factors:
- 1 km = 1000 meters
- 1 hour = 3600 seconds

The conversion formula is:
\[ \text{Speed in m/s} = \text{Speed in km/h} \times \frac{1000 \text{ m}}{3600 \text{ s}} \]

Substituting the value we calculated:
\[ \text{Speed in m/s} = 31.5 \times \frac{1000}{3600} \]

### Step 4: Simplify the conversion
Calculating the conversion:
\[ \text{Speed in m/s} = 31.5 \times \frac{1000}{3600} \]
\[ = 31.5 \times \frac{1}{3.6} \]
\[ = \frac{31.5}{3.6} \]

### Step 5: Perform the division
Now we perform the division:
\[ \frac{31.5}{3.6} = 8.75 \text{ m/s} \]

### Final Answer
The average speed of the car is **8.75 meters per second**.

---