A missile travels at a speed of 1440 km/h. How many metres does it travel in one second?

Introduction / Context:
This problem focuses on converting a speed given in kilometres per hour into the distance covered per second in metres. Such unit conversion questions are standard in aptitude tests and help reinforce the understanding of how different time and distance units relate to each other. They also train the habit of checking units carefully before performing numerical calculations, which is essential in physics and engineering problems.

Given Data / Assumptions:

Missile speed = 1440 km/h.
We are asked for the distance travelled in one second.
We assume the missile maintains a constant speed during this time.
1 kilometre = 1000 metres and 1 hour = 3600 seconds.

Concept / Approach:
To find the distance in one second, it is convenient to first convert the speed from kilometres per hour to metres per second using a standard conversion factor. The key relationship is:
1 km/h = (1000 / 3600) m/s Once we convert 1440 km/h to m/s, the distance travelled in one second is simply that speed value, because distance = speed * time and the time is exactly one second. This makes the final step immediate once the unit conversion is completed correctly.

Step-by-Step Solution:
Step 1: Use the conversion factor. 1440 km/h = 1440 * (1000 / 3600) m/s. Step 2: Simplify the fraction 1000 / 3600. 1000 / 3600 = 1 / 3.6. Step 3: Compute the speed in m/s. 1440 * (1000 / 3600) = 1440000 / 3600. 1440000 / 3600 = 400. So the missile's speed is 400 m/s. Step 4: Distance in one second. distance = speed * time = 400 * 1 = 400 metres.

Verification / Alternative check:
We can mentally check the magnitude. A speed of about 360 km/h corresponds to roughly 100 m/s, because 360 km/h is known to be 100 m/s. Since 1440 km/h is four times 360 km/h, its speed in m/s should be four times 100 m/s, which is 400 m/s. This quick ratio argument matches the detailed computation and confirms that 400 metres in one second is correct.

Why Other Options Are Wrong:
Options a (374 metres), b (385 metres), and c (394 metres) are all close to 400 but do not correspond to any accurate conversion of 1440 km/h to m/s. They are likely included to trap students who make arithmetic rounding errors or approximate incorrectly. Only option d, 400 metres, precisely matches the correct conversion and the logical ratio check with 360 km/h.

Common Pitfalls:
Typical mistakes include dividing by 60 instead of 3600, forgetting to multiply by 1000, or mixing up whether to multiply or divide by the conversion factor. Another error is to compute 1440 / 3600 and forget to multiply by 1000 later, which yields a value that is too small. Always write out the conversion clearly as (km/h) * (1000 m / 1 km) * (1 h / 3600 s) and cancel units step by step to avoid confusion.

Final Answer:
Hence, the missile travels 400 metres in one second.