Percentages

Percents can be tricky. Here are some problems that point out some of the pitfalls of percents.

Discussion

1. 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?

2. 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'?

3. 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?

Journal assignment for Tuesday 6 April

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?