If you invest $3,900 at a 7.83% simple annual interest rate, approximately how long will it take for you to have a total of $10,000? a. 12 years b. 15 years c. 20 years d. 30 years

Apply simple interest formula

future value = present value (1+n*rate)

n=number of years

rate = annual interest rate in decimal

Plug in values,

10000=3900 (1+0.0783*t)

1+0.0783t=10000/3900

t = (10000/3900-1) / 0.0783

=19.98 years.

With compound interest, future value=present value (1+rate/n) ^ (nt)

n=1, rate=0.0783, future value=10000, present value=3900,

t=log (10000/3900) / log (1.0783) = 12.49 years.