SOLUTION: A parent raises a child’s allowance by 15% each year. If the allowance is $3 now, when will it reach $15? I've tried several ways to complete this question but none have seemed

Algebra ->  Finance -> SOLUTION: A parent raises a child’s allowance by 15% each year. If the allowance is $3 now, when will it reach $15? I've tried several ways to complete this question but none have seemed      Log On


   

Question 274777: A parent raises a child’s allowance by 15% each year. If the allowance
is $3 now, when will it reach $15?
I've tried several ways to complete this question but none have seemed to work. The only answer that seems like it could work was 11 1/2 yrs. How do you work this problem out and get a real answer? your help is much appreciated.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A parent raises a child’s allowance by 15% each year. If the allowance
is $3 now, when will it reach $15?
:
How about this?
t = no. of years for this to happen
:
3*(1.15^t) = 15
divide both sides by 3
1.15^t = 15%2F3
1.15^t = 5
:
use logs here
log(1.15^t) = log(5)
which is
t*log(1.15) = log(5)
:
t = log%285%29%2Flog%281.15%29; enter into your calc
t ~ 11.5 years, which is what you said