SOLUTION: A 8-inch sunflower is planted in a garden and the height of the sunflower increases exponentially, increasing by 15% per day. a. Write a function f that determines the height o

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: A 8-inch sunflower is planted in a garden and the height of the sunflower increases exponentially, increasing by 15% per day. a. Write a function f that determines the height o      Log On


   

Question 1125095: A 8-inch sunflower is planted in a garden and the height of the sunflower increases exponentially, increasing by 15% per day.
a. Write a function f that determines the height of the sunflower (in inches) in terms of the number of days t since it was planted.
f(t)=
b. How many days after it was planted will the sunflower be 25 inches tall?
c. How many days after it was planted will the sunflower be 138 inches tall?
Answer by fcabanski(1391) About Me  (Show Source):
You can put this solution on YOUR website!
N = 8(1+.15)^d d is the number of days, and N is the height after d days.


b. 25 = 8(1.15)^d
log25 = log(1.15)^d = dlog(1.15)

log25/log1.15 = d = 23.03 days = around 23 days.


c. Likewise for 138 inches it's log138/log1.15 = about 35 days