Final answer:
Conversions between measurement systems are best done using unit conversion factors and dimensional analysis, applying correct ratios, and understanding relationships between units within a system.
Step-by-step explanation:
Conversions between systems of measurement can best be computed by using unit conversion factors and dimensional analysis. When converting measurements from one system to another, such as converting a length in kilometers in the International System of Units (SI) to miles in the customary system primarily used in the United States, it's important to use the correct conversion factor. This factor is a ratio that represents how a unit in one system relates to a unit in another system. For example, to convert inches to centimeters, the conversion factor is 2.54 cm equals 1 inch. When converting within the same system, such as from meters to kilometers in SI, a basic understanding of the metric system's base-10 structure is essential. There's also the need to understand the relationship between different units of measurement in the customary system, like how many feet are in a mile.