How do you solve 120=100(1+(.03212))12t?

2 Answers
Nov 14, 2015

Use logarithms.

Explanation:

Divide both sides by 100: 1.2=(1+(.03212))12t
Simplify the inside: 1.2=(1.002¯6)12t
Convert into a logarithm: log1.21.002¯6=12t
Change of base formula: log1.002¯6log1.2=12t
Divide both sides by 12: log1.002¯612log1.2=t

Nov 14, 2015

t=ln(65)12ln(1+.03212)

Explanation:

We will be using the property of logarithms that
ln(xn)=nln(x)
(this is very useful for solving for variables in exponents)

120=100(1+.03212)12t

120100=65=(1+.03212)12t

ln(65)=ln((1+.03212)12t)

ln(65)=12tln(1+.03212) (by the property stated above)

Now, solving for t gives

t=ln(65)12ln(1+.03212)