I am an advocate for NEVER writing a
calculation/math question as a tossup, no matter how easy it is.
At the Great Lakes Regional Academic Championship
(plug for Case Western Reserve University/Cleveland OH)
and the National Scholastics Championship (2000
Furman University), we give teams the "option" of
choosing a math calculation question in one section of
game play. At least we have found that this works
quite well.
Of course, this doesn't mean we
don't have math calculation questions anywhere else
during a round, but they won't come up as tossups.