Consumer Numeracy
Jerry Johnson
University of Nevada, Reno
Quantitative literacy is very important when it comes to being an informed
consumer. Quantitatively literate consumers understand how to select the best values and
they are less likely to be cheated.
In deciding the best buy on a pizza one needs to be aware that the area of a circle is p r2,
which is the same thing as p / 4 = d 2 where d is the diameter.
This means that the area is
proportional to the square of the radius (or the square of the diameter). Thus, doubling the
diameter quadruples the area. Pizza sizes are usually given in terms of their diameters. By
the way, p is about 3.14.
In considering the price of carpet, one might need to know how to convert between
square feet and square yards. (One square yard is nine square feet.) Other conversions are
useful as well, such as between liters and ounces (one liter is about 33.82 ounces).
The mathematics is arithmetic, calculating the area of a rectangle and a circle and, conversion of units of
measurement.