A man seeinga lightningstarts countingseconds, until he hears thunder. He then claims to have found an approximate but simple rule that if the count of second is divided by an integer, the result directly gives, in km, the distance of the lightning sotirce. Whatis theinteger ? (Velocityofsound inair = 330 m/s)

Explanation

To solve the problem, we need to find the integer that allows us to convert the time (in seconds) counted after seeing lightning into the distance (in kilometers) to the lightning source.

### Step-by-Step Solution:

1. **Understanding the Problem**:
The man counts the seconds from seeing the lightning until he hears the thunder. We need to relate this time to the distance of the lightning in kilometers.

2. **Using the Velocity of Sound**:
We know the velocity of sound in air is given as 330 m/s.

3. **Relating Distance, Velocity, and Time**:
The relationship between distance (L), velocity (V), and time (T) is given by the formula:
\[ L = V \times T \]
Here, L is the distance in meters, V is the velocity of sound (330 m/s), and T is the time in seconds.

4. **Converting Distance to Kilometers**:
Since we want the distance in kilometers, we need to convert meters to kilometers. We know that:
\[ 1 \text{ km} = 1000 \text{ m} \]
Therefore, if we express L in kilometers, we can write:
\[ L = \frac{V \times T}{1000} \]

5. **Substituting the Values**:
Substituting the velocity of sound into the equation:
\[ L = \frac{330 \times T}{1000} \]

6. **Simplifying the Equation**:
Simplifying the equation gives:
\[ L = 0.33 \times T \]

7. **Finding the Integer**:
To find the integer that relates the time in seconds to the distance in kilometers, we can rewrite the equation:
\[ L = \frac{T}{3} \]
This means that if we divide the time (T) by 3, we get the distance (L) in kilometers.

8. **Conclusion**:
Therefore, the integer that the man uses to divide the count of seconds to find the distance to the lightning source is:
\[ \text{Integer} = 3 \]

### Final Answer:
The integer is **3**.