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U have $100,000 to invest & wish to double that amount. Using the CIF, find the the...

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tame25 | Student, Grade 9 | (Level 1) Honors

Posted February 15, 2012 at 3:20 PM via web

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U have $100,000 to invest & wish to double that amount. Using the CIF, find the the years it take to double at rate of 12% p.a. Determine to the nearest whole number of years, the length of time it will take to do this using the CIF. (CIF)stands for 'Compound interest formula': A=P(1+R/100)^N Amount(A) Principal(P) Rate of interest(R) Periods(N)

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nathanshields | High School Teacher | (Level 1) Associate Educator

Posted February 15, 2012 at 7:16 PM (Answer #1)

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200000=100000(1+0.12)^N

2=(1.12)^N

Solving for an exponent... time to break out the logs!

log 2 = log (1.12^N) = N log 1.12

Did you remember that log rule? `logA^x=xlogA`

N = log 2 / log 1.12 = 6.12 yrs (so 7 years).

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