Priscilla invests $10,000 in an account that compounds interest continuously and earns 11%. How long will it take for her money to double? Round to the nearest tenth of a year.

Respuesta :

Answer:

Step-by-step explanation:

When the interest compounds continuously, our formula is

[tex]A(t)=Pe^{rt}[/tex]

If we start with 10000 and are looking for how long, t, it takes to double, we are looking for how long it will take for our account to have 2 times 10000.  That's 20000.  Therefore, our equation is

[tex]20000=10000e^{.11t}[/tex]

Divide both sides by 10000 to get

[tex]2=e^{.11t}[/tex]

Take the natural log of both sides to "undo" that e:

[tex]ln(2)=ln(e^{.11t})[/tex]

Again, since ln and e undo each other what we have now is

ln(2) = .11t and

[tex]\frac{ln(2)}{.11}=t[/tex] so

t = 6.3 years