Solve for the unknown number of years in each of the following:

Note: Do not round intermediate calculations and round your answers to $2$ decimal places, e$.$g$.,32\mathrm{.}16.$

$\backslash$table$[[$Present Value,Years,Interest Rate,Future Value$],[$$$,10,\%,$$$,1,155],[300,,8,\%,3,750],[1,991,,13,\%,387,620],[32,905,,20,\%,199,724],[32,600,,,,]]$