



 
Hi John, The usual reason is that lowestterms notation makes it easier to answer the question "are these fractions equal?" (And, of course, "is this the right answer?") However, there are cases where this is not done, often where one might also want to answer the question "which of these is bigger?" In this case the use of a standard denominator is common. "95%" rather than "19/20" Good hunting!  


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