The new denominator is the same as the denominator of the improper fraction.
From the en.wikipedia.org
An improper fraction is another way to write a whole plus a part.
From the en.wikipedia.org
The resulting sum is the improper fraction.
From the en.wikipedia.org
In the case where they are the fraction of a government's fossil fuel revenue that it is willing to spend on token fossil fuel replacements, such a fraction is exceptionally improper.
From the guardian.co.uk
Sixth-graders used fraction bars to demonstrate converting between mixed numbers and improper fractions.
From the indianolarecordherald.desmoinesregister.com
When the numerator and the denominator are both positive, the fraction is called proper if the numerator is less than the denominator, and improper otherwise.