Completion

1)1
2)conversion factor
3)change
4)Dimensional anaylsis
5)

Whenever two measurement are equal, or equivalent, a ratio of these two measurements will equal ___1____. A ratio of equivalent measurement is called a ___2___. When a measurement is multiplied by a conversion factor, the value of the measurement ___3____. In ____4___, the units that are a part of the measuerements are used to help solve the problem. The form of the conversion factor that is used is the one in which the unit of the ___5____ is the denominator.

I think 1, 2, 3, and 4, are ok.
For 5, let's look at a conversion.
12 inches = 1 foot
conversion factor = 12 in/1 ft
OR 1 ft/12 inches.

given: 3 ft.
convert to inches.

3 ft x (12 inches/1 ft) = 36 inches.
So the denominator is the part of the conversion factor that must cancel and that is the "given" or "the beginning unit" or some word like that. You probably had that in class or its in your notes. Note that we started with ft and we want to cancel the ft so ft must be on the bottom.

The missing word in the sentence is "given." In dimensional analysis, the units that are a part of the measurements are used to help solve the problem. The form of the conversion factor that is used is the one in which the unit of the "given" is the denominator. In the example given, we want to convert 3 ft to inches. The conversion factor is 12 inches/1 ft, and we multiply it by 3 ft. In order for the ft unit to cancel out, it must be in the denominator of the conversion factor.