Explanation: In the context of measuring distances, it is essential to understand the appropriate units of measurement based on the scale of the distance. The metric system provides a range of units, including millimetres (mm), centimetres (cm), metres (m), and kilometres (km), each suitable for different scales of measurement.
Millimetres and centimetres are used for small-scale measurements, such as the dimensions of objects that can be held in one's hand. For example, the thickness of a book or the length of a pencil would be measured in millimetres or centimetres.
Metres are used for medium-scale measurements, such as the height of a person or the length of a room. However, when it comes to measuring distances between cities or countries, metres are not practical due to the large numbers involved.
Kilometres are the standard unit for measuring long distances, such as the distance between two cities or the length of a road. One kilometre is equal to 1000 metres, making it a more manageable unit for large-scale measurements. For instance, the distance from Delhi to Patna, two major cities in India, is approximately 1000 kilometres. Using kilometres for this measurement is appropriate because it provides a clear and concise representation of the distance.
Understanding the appropriate unit of measurement is crucial for accurately conveying information about distances. Using the wrong unit can lead to confusion and misinterpretation. For example, if the distance from Delhi to Patna were expressed in millimetres, it would be an impractically large number (1,000,000,000 mm), making it difficult to comprehend and use effectively.
In summary, the choice of unit for measuring the distance from Delhi to Patna is based on the scale of the distance. Kilometres are the correct unit because they provide a practical and easily understandable representation of the distance between two major cities.