Question

You want to invest

Answer 1

Using the equation         >    A  =  Pe^rt

20000  =    10000e^0.1t    >       10%  =  0.1
 2  = e^0.1t
log 2  =    log e^0.1t               >     log to the base e
log 2  =  0.1t * 1              log e to the base e  =1
0.6931 = 0.1t
t =   6.931
   =    7 years