SOLUTION: How do I solve the following word problems: 1. If the population of a city is 178500 and it is growing at the rate of 2.1% per annum, in how many years will the population be 21

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Question 388778: How do I solve the following word problems:
1. If the population of a city is 178500 and it is growing at the rate of 2.1% per annum, in how many years will the population be 210000?

Found 2 solutions by stanbon, ankor@dixie-net.com:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
If the population of a city is 178500 and it is growing at
the rate of 2.1% per annum, in how many years will the
population be 210000?
---
A(t) = 178500*(1+0.021)^t
----
210,000 = 178500*1.02^t
1.02^t = 1.17647
---
t = log(1.17647)/log(1.02)
---
t = 8.207 years
======================
Cheers,
Stan H.

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
. If the population of a city is 178500 and it is growing at the rate of 2.1% per annum,
in how many years will the population be 210000?
:
Let t = number of yrs to reach 210,000
:
178500*1.021^t = 210000
Divide both sides by 178500
1.021^t = 210000%2F178500
1.021^t = 1.17647
Use logs here
t*log(1.021) = log(1.17647)
t = log%281.17647%29%2Flog%281.021%29
t = 7.8 yrs
:
:
Check solution on a calc: enter: 178500*1.021^7.8 ~ 210,000