+0  
 
+1
364
1
avatar+232 

Every June 1, an ecologist takes a census of the number of wrens in a state park. She noticed that the number is decreasing by 40% each year. If this trend continues, in what year will the census show that the number of wrens is less than 10% of what it was on June 1, 2004?

 Jun 10, 2018
 #1
avatar
+2

Let the number of wrens on June 1, 2004 = W
< 10%W = W x [1 - 0.4]^n, solve for n
<10% = [0.60]^n     take the log of both sides
n = Log(0.099) / Log(0.6)
n = 4.527 years =~4.5 years after 2004.

 Jun 10, 2018

42 Online Users