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Percents can be tricky. Here are some problems that point out some
of the pitfalls of percents.
- Which would be better: to become 50%richer and then
50%poorer, or to become 50%poorer and then 50%richer, or to have your fortune remain constant?
- The recipe for pizza in Laurel's Kitchen says: `Let the
dough rise only once, about hours'. How long
should you let the dough rise if you use Fleischmann's
Rapid Rise Yeast, whose package states that it `rises 50%faster'?
- A series of 12 monthly Tantalene injections ($450apiece)
reduces the 5-year death toll from lemon meringue disease
from 3 per 10,000,000 to 1 per 10,000,000. Suppose that
you work for an advertising agency representing the
makers of Tantalene, and your job is to get doctors to
prescribe Tantalene injections for as many of their patients
as possible. How would you express this change in
mortality rate using percents?
In criminal trials, the defendant can only be convicted if guilt is
proven beyond a resaonable doubt. What probability would you
associate with the term `reasonable doubt'? Would it be 95%?99%?99.9%?99.9999%?Justify your answer. Would it depend on
the particular crime, or the possible punishment? How many persons
convicted of murder in this country in the past ten years do you
suppose are completely innocent?