Consider a $100 investment earning 12% compounded quarterly. how long will it take to triple your money? round your answer to the nearest tenth of a year.

Summarizing the question,

Principle (P) = $100

Rate (r) = 12%=0.12

Amount (A) = 3*P=$300

Time=t=?

n=no of times the interest is compouned per year=4

Then,

A=P{ (1+r/n) }^ (n*t)

or, 300=100*{1+0.12/4}^ (4*t)

or, 300/100 = (1+0.03) ^ (4*t)

or, 3=1.03^ (4*t)

Taking log on both sides,

log3=log[ (1.03) ^ (4*t) ]

or, log3 = (4*t) * log (1.03)

or, 4t=log3/log (1.03)

or, t=log3/[4*log (1.03) ]

or, t=9.29175 ...

t=9.3 years ANS!