What is the length of the ridge in a hip roof that is 42 feet long and 24 feet wide?

In the context of a hip roof, which has slopes on all four sides rather than two, the term "ridge" refers to the horizontal line at the peak where the sloping sides meet. The length of the ridge aligns with the longest side of the structure, which is generally the length of the building along its longest span.

In this scenario, the dimensions provided indicate that the building is 42 feet long and 24 feet wide. Therefore, the ridge, being the line at the peak of the roof that runs along the length of the building, will indeed be 42 feet. This makes the correct answer reflect the actual dimension of the building that corresponds to the ridge length, which is the longitudinal side, reinforcing the standard concept of how hip roofs are designed.

As such, the other measurements do not pertain to the roof's ridge length, as they either reflect the width of the building or are not relevant to the ridge dimension itself.