Final answer:
A ratio is a comparison of two quantities by division, correctly filled in as option C) ratio. It can be expressed in various forms and is essential for understanding proportions, unit rates, scale factors, and conversion factors.
Step-by-step explanation:
A ratio is a comparison of two quantities by division. The correct term to fill in the blank in the sentence is C) ratio. A ratio provides the relative size of one quantity compared to another and can be expressed in various forms such as fractions, with a colon, or with the word 'to'. For example, the ratio of two to three can be written as 2/3, 2:3, or '2 to 3'. Ratios are foundational in understanding proportions, unit rates, and scale factors, which are all applications of ratios in different contexts.
A fraction, on the other hand, is a part of a whole represented by a numerator and a denominator. When expressed as a ratio, the fraction can indicate a part in comparison to the whole, such as one half represented as 1/2. Similarly, a conversion factor is a special type of ratio that equates two different units of measure, enabling the conversion from one to the other, and it always equals one because it contains the same quantity in the numerator and the denominator.
Understanding the concept of ratio extends to practical applications, such as determining the unit scale on a map, where a certain length on the map corresponds to a specific distance in reality. This concept is vital in real-world applications such as architecture, engineering, and geography.