Question 869067
Balance is {{{p(1+r)^t}}} for time t in years.


t=1, {{{p(1+r)^1}}}.
t=3, {{{p(1+r)^3}}}.
You would expect to use r as a decimal as you say.


The ratio of balances is {{{(p(1+r)^3)/(p(1+r)^1)=highlight((1+r)^2)}}}.
Do you have a known value of the ratio?
If you know for some constant, k, that {{{(1+r)^2=k}}}, then you have {{{(1+r)^2-k=0}}.
{{{(1+r)^2=k}}}
{{{1+r=sqrt(k)}}}
{{{highlight(r=-1+sqrt(k))}}}