how many years will it take to double $1000 at 20% interest.

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Guest Apr 14, 2015

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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.

Melody Apr 14, 2015

Melody · Answer 1 · 2015-04-14T02:47:11

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.

civonamzuk · Answer 2 · 2015-04-14T04:20:25

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Melody · Answer 3 · 2015-04-15T07:23:58

Hi Civonamzuk,

What you have done may well be correct but I don't follow your logic.

Could you please add in some more working ?