A sum amounts to double in 20 years by C.I, in how many years it will triple with same rate compound interest?

with out using log table.

A sum amounts to double in 20 years by C.I, in how many years it will triple with same rate compound interest?
2=(1+i)^20


log2=20*log(1+i)


.301=20*log(1+i)


log(1+i)=.01506


1+i=1.03526


i=0.03526





3=(1+i)^x


log3=x*log(1+i) from line 4


.4777=x*0.01506


x=31.7
Reply:oh i would love to help but dont exactly know how...sorry.