ABC26GN4049 · Simple Interest
Subject: General Aptitude · Chapter: Simple Interest · Exam: 2006 · Marks: · Difficulty:
A sum of money at simple interest doubles in 7 years. It will become four times in:
(a)18 years
(b)21 years
(c)38 years
(d)42 years
Answer
Explanation
Let $\operatorname{sum}=₹ x$. Then, S.I. $=₹ x$. $\therefore \quad$ Rate $=\left(\frac{100 \times x}{x \times 7}\right) \%=\frac{100}{7} \%$. Now, sum $=₹ x$, S.I. $=₹ 3 x$, Rate $=\frac{100}{7} \%$. ∴ Time $=\left(\frac{100 \times 3 x}{x \times \frac{100}{7}}\right) \mathrm{yrs}=21$ years.
Explanation as extracted from the printed page; notation may be imperfect.
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