MCQ
At what rate percent per annum simple interest will a sum be double itself in $8$ years?
- A$15\%$
- B$12\%$
- ✓$12.5\%$
- D$17.5\%$
✓
Answer
Correct option: C.
$12.5\%$
Let sum $= P$ and Interest rate $= R$
Now Simple Interest $= P$
Simple Interest $=\frac{\big(\text{sum}\times\text{interest rate}\times\text{time}\big)}{100}$
$\Rightarrow\text{P}=\frac{(\text{P}\times8\times\text{R})}{100}$
$\Rightarrow2=\frac{8\text{R}}{100}$
$\Rightarrow8\text{R}\times100$
$\Rightarrow\text{R}=\frac{100}{8}$
$\Rightarrow\text{R}=\frac{25}{2}$ $(100$ and $8$ is divided by $4)$
$\Rightarrow\text{R}=12.5\%$
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