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| Question 1198853:  Your parents will retire in 18 years. They currently have $250,000, and they think they will need
 $1 million at retirement. What annual interest rate must they earn to reach their goal, assuming
 they don’t save any additional fund?
 Answer by Theo(13342)
      (Show Source): 
You can put this solution on YOUR website! formula to use is f = p * (1 + r) ^ n f is the future value
 p is the present value
 (1 + r) is the annual growth rate.
 n is the number of years.
 
 formula becomes:
 1,000,000 = 250,000 * (1 + r) ^ 18
 divide both sides of the equation by 250,000 to get:
 4 = (1 + r) ^ 18
 take the 18th root of both sides of the equation to get:
 4 ^ (1/18) = (1 + r)
 solve for (1 + r) to get:
 1 + r = 1.080059739
 that's the annual growth rate.
 
 confirm by replacing (1 + r) in the equation with that to get:
 f = 250,000 * 1.080059739 ^ 18 = 1,000,000
 this confirms the value of (1 + 4) is correct.
 
 1 + r is the annual growth factor.
 subtract 1 from that to get the annual growth rte.
 that would be .080059739.
 multiply that by 100 and round to decimal places to get 8.01% growth rate per year.
 
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