Posted by Beverly on Saturday, April 2, 2011 at 9:09pm.
18 = 3.5(1.12)^n
5.142857 = 1.12^n
take log of both sides and use log rules....
n = log 5.142857/log 1.12 = 14.45
so after 14 years the allowance will be below $18
but after 15 years it will be over $18
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