http://www.ck12.org Chapter 1. Introduction to Physical Science
Circle Graphs
The data inTable1.7 shows the percent of all U.S. tornadoes by tornado strength for the years 1986 to 1995. In this
table, tornadoes are rated on a scale called the F scale. On this scale, F0 tornadoes are the weakest and F5 tornadoes
are the strongest.
TABLE1.7: Percent of Tornadoes by Strength in the U.S. (1986–1995)
Tornado Scale(F-scale rating) Percent of all U.S. Tornadoes
F0 55.0%
F1 31.6%
F2 10.0%
F3 2.6%
F4 0.7%
F5 0.1%Circle graphs are used to show percents (or fractions) of a whole, such as the percents of F0 to F5 tornadoes out of
all tornadoes. Therefore, a circle graph is a good choice for the data in the table. The circle graph below displays
these data.
Q:What if theTable1.7 on tornado strength listed the numbers of tornadoes rather than the percents of tornadoes?
Could a circle graph be used to display these data?
A:No, a circle graph can only be used to show percents (or fractions) of a whole. However, the numbers could be
used to calculate percents, which could then be displayed in a circle graph. If you need a refresher on percents and
fractions, go to this URL: http://www.mathsisfun.com/decimal-fraction-percentage.html.
Line Graphs
Consider the data inTable1.8. It lists the number of tornadoes in the U.S. per month, averaged over the years 2009
to 2011.