HP 10bii Manuale Utente

 

 

Is it raining again in Seattle… 

Wait, you mean San Antonio 

 – Article – 

 
Here are two quick problems involving fractions and number patterns.  Both of these problems involve 

trends in the average annual rainfall of a US city.  These trends are called 50-year trends and are based on 

data gathered by the National Oceanic and Atmospheric Administration (NOAA). 

 
Two Rainy Cities? 

Seattle has long been known for its cloudy, rainy weather; in fact, one of its nicknames is the Rainy City.  

Since 1961, the average annual precipitation has been just less than 38 2/5”. San Antonio, on the other 
hand, had an average annual precipitation of just less than 30 1/2" over the same period.  According to 

NOAA, San Antonio has a 50-year trend of increasing annual precipitation.  If the trend continues, 

eventually San Antonio will have greater annual precipitation than Seattle currently has.  The trend is an 

additional 1 1/8” of precipitation per decade.  Use this information to fill in the first column in the table 

below.  Then estimate the year in which San Antonio’s annual precipitation is greater than Seattle’s current 
38 2/5”. 

 
Two Trends 
Seattle, in the meantime, has its own 50-year annual precipitation trend.  According to NOAA, the trend 

for Seattle is a decreasing one.  Seattle gets 2/3” less annual precipitation each decade.  With Seattle’s 

annual precipitation decreasing and San Antonio’s increasing, at some point the two cities will have the 

same annual precipitation.  Fill in the second column of the table below with rainfall figures.  Estimate the 
year in which both cities have the same annual precipitation.  Show your estimate of the number of inches 

of rainfall that year as well.   

 

2

1

30

 

5

2

38

 

 

 

 

 

 

 

 

 

 

 

 
 
Teacher Notes 

These short activities take global warming and climatic change as topics to generate student interest in 
mixed numbers and number patterns.   

 

 

 

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