+118613 how many years will it take to double $1000 at 20% interest.
$$\\2000=1000(1.2)^n\\
2=1.2^n\\
log2=log(1.2^n)\\
log2=nlog1.2\\
n=log2\div log 1.2$$
$${\frac{{log}_{10}\left({\mathtt{2}}\right)}{{log}_{10}\left({\mathtt{1.2}}\right)}} = {\mathtt{3.801\: \!784\: \!016\: \!923\: \!930\: \!7}}$$
almost 4 years.
+118613 how many years will it take to double $1000 at 20% interest.
$$\\2000=1000(1.2)^n\\
2=1.2^n\\
log2=log(1.2^n)\\
log2=nlog1.2\\
n=log2\div log 1.2$$
$${\frac{{log}_{10}\left({\mathtt{2}}\right)}{{log}_{10}\left({\mathtt{1.2}}\right)}} = {\mathtt{3.801\: \!784\: \!016\: \!923\: \!930\: \!7}}$$
almost 4 years.
