A sum of money doubles itself at compound interest in 15 years. In how many years will it become eight times? · ABC26GN4138
Subject: General Aptitude · Chapter: Compound Interest
A sum of money doubles itself at compound interest in 15 years. In how many years will it become eight times?
Answer
No answer key was printed for this question.
Explanation
$P\left(1+\frac{R}{100}\right)^{15}=2 P \Rightarrow\left(1+\frac{R}{100}\right)^{15}=\frac{2 P}{P}=2$ Let $P\left(1+\frac{R}{100}\right)^{n}=8 P \Rightarrow\left(1+\frac{R}{100}\right)^{n}=8=2^{3}=\left\{\left(1+\frac{R}{100}\right)^{15}\right\}^{3}$ [using (i)] $$\Rightarrow\left(1+\frac{R}{100}\right)^{n}=\left(1+\frac{R}{100}\right)^{45} \Rightarrow n=45 .$$ Thus, the required time $=45$ years.
Explanation as extracted from the printed page; notation may be imperfect.