In one km race A beats B by 5 seconds or 40 metres. How long does B take to run the kilometre ?

Options

A. 125 sec
B. 120 sec
C. 130 sec
D. None of these

Answer

To solve the problem of how long B takes to run the kilometer, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Information Given**:
- A beats B by 5 seconds or 40 meters in a 1 km race.
- This means when A finishes the race, B has not yet completed the full distance of 1 km.

2. **Finding the Time for B to Cover 40 Meters**:
- Since A beats B by 5 seconds, this means that B takes 5 seconds longer than A to finish the race.
- In the time A takes to finish the race, B has only covered 960 meters (1000 meters - 40 meters).

3. **Calculating B's Speed**:
- If B covers 40 meters in 5 seconds, we can find B's speed.
- Speed of B = Distance / Time = 40 meters / 5 seconds = 8 meters/second.

4. **Finding the Time for B to Cover 1 Kilometer**:
- Now, we need to find out how long it takes for B to cover the entire 1000 meters.
- Time = Distance / Speed = 1000 meters / 8 meters/second = 125 seconds.

5. **Conclusion**:
- Therefore, B takes 125 seconds to run the kilometer.

### Final Answer:
B takes **125 seconds** to run the kilometer.

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