SOLUTION: How long would it take for $100 to become $1000 if it is invested at an 8% annual interest rate that is compounded quarterly?

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Question 154536: How long would it take for $100 to become $1000 if it is invested at an 8% annual interest rate that is compounded quarterly?
Answer by AnlytcPhil(1806) About Me  (Show Source):
You can put this solution on YOUR website!
How long would it take for $100 to become $1000 if it is invested at an 8% annual interest rate that is compounded quarterly?


A+=+P%281%2Br%2Fn%29%5E%28nt%29

where P = beginning amount = 100
      A = final amount = 1000 
      r = rate expressed as a decimal = .08
      n = 4 (quarterly means compounded 4 times a year)
      t = ? (number of years, the unknown)

1000+=+100%281%2B.08%2F4%29%5E%284t%29

1000+=+100%281%2B.02%29%5E%284t%29

1000+=+100%281.02%29%5E%284t%29

Divide both sides by 100

10+=+%281.02%29%5E%284t%29

Take logs of both sides:

log%2810%29+=+log%281.02%5E%284t%29%29  

Use the rule of logs:  log%28A%5EC%29=C%2Alog%28A%29

log%2810%29+=+4t%2Alog%281.02%29

Divide both sides by (4*log(1.02))

log%2810%29%2F%284log%281.02%29%29+=+t

29.06918686 years.

Edwin