ABC26GN4191 · Compound Interest
Subject: General Aptitude · Chapter: Compound Interest · Exam: 2010 · Marks: · Difficulty:
A sum of ₹ 12,000 deposited at compound interest becomes double after 5 years. After 20 years, it will become :
(a)₹ 96,000
(b)₹ 1,20,000
(c)₹ 1,24,000
(d)₹ 1,92,000
Answer
Explanation
$12000 \times\left(1+\frac{R}{100}\right)^{5}=24000 \Rightarrow\left(1+\frac{R}{100}\right)^{5}=2$ $$\begin{aligned} & \therefore\left[\left(1+\frac{R}{100}\right)^{5}\right]^{4}=2^{4}=16 \\ & \Rightarrow\left(1+\frac{R}{100}\right)^{20}=16 \\ & \Rightarrow P\left(1+\frac{R}{100}\right)^{20}=16 P \\ & \Rightarrow 12000\left(1+\frac{R}{100}\right)^{20}=16 \times 12000=192000 \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.
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