How many tornadoes occur on average per year in this area?

• A. 1 per year
• B. 5 per year
• C. 3 per year
• D. 7 per year

Answer: (C)

The idea is to use the long-term average of annual tornado counts to describe how often the area experiences tornadoes. To get this average, you add up the number of tornadoes each year over many years and divide by the number of years. This mean value shows the typical frequency, smoothing out the highs and lows from year to year.

For this area, historical records show about three tornadoes per year on average. That means, when you look at many years of data, the total number of tornadoes divided by the number of years comes out around three. Some years have more, some have less, but the balance over time centers near three.

Choosing one per year would imply the area is less active than the usual record suggests, while five or seven per year would imply a much more active pattern than the long-term average indicates. The average around three best represents the common level of activity across many years.