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Math Help???????

Use the formula A=P ( 1+ r/n)nt  to solve the compound interest problem 
Find how long it takes a $1700 investment to earn $500 interest if it is invested at 7% compounded quarterly.
$500 interest will be earned in approximately ????? years 

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Regina G. | Biotech Grad with Homeschool Experience, Math and Science FocusBiotech Grad with Homeschool Experience,...
5.0 5.0 (279 lesson ratings) (279)
You need to rearrange to isolate the variable t.
Starting with the formula
A = P (1+r/n)nt
Isolate term with unknown exponent
A/P = (1+r/n)nt
It might be useful to plug the values in, at this step, to simplify the work.
(1700+500)/1700 = (1 + .07/4)4t
1.29412 = (1.0175)4t
Rearrange a little, to simplify, a little more, moving the constant part of the exponent into the parentheses
1.29412 = (1.01754)t
Evaluate the statement in parentheses
1.29412 = (1.07186)t
Take log of both sides to eliminate the exponent.
log 1.29412 = log 1.07186t
Use power property of exponents
log 1.29412 = t * log 1.07186
Isolate the variable
t = log 1.29412/log 1.07186
Evaluate, then round to appropriate figures.