A fraction makes sense only if it refers to a particular scale or unit. One half of a unit square can represent different areas depending on the size of the unit. If two unit squares do not have the same scale, a unit fraction will not have the same size area.
What to look for
Students should reflect on what they know about equivalent fractions, comparing fractions, and adding and subtracting fractions, noting that these operations only make sense if the fractions represent the same whole.
A box of granola bars contains 18 bars. How many bars will be in (2/3) of the box?
Answer: 12 bars