How many valid and invalid classes exist for a continuous range in equivalent partitioning?

In the context of equivalence partitioning for a continuous range, there are generally three types of classes: valid and invalid partitions. For a continuous range of valid input values, there is one valid class that encompasses all acceptable values within that range. Conversely, invalid classes will consist of the values that lie outside of this continuous valid range.

For example, if considering an input range of ages from 1 to 100, the valid class would include all integers within this range (1 to 100). The invalid classes would then include two segments: one for ages below the range (e.g., 0 and negative numbers) and one for ages above the range (e.g., 101 and above). Thus, if we categorize these classes, we see we have one valid class (1 to 100) and two invalid classes (below the range and above the range).

This reasoning explains why the correct classification consists of one valid class and two invalid classes, aligning with the principal rules of equivalence partitioning.