Question

At what rate percent per annum at simple interest, will a sum triple itself in $16$ years?
(a) $12\%$
(b) $10.5\%$
(c) $11.5\%$
(d) $12.5\%$

Answer 1

Correct option is D. $12.5\%$

Let the sum be $P$, Rate of interest be $R\%$ and Time be $16$ years

Therefore, Amount $=3\times P=3P$

Hence, $SI=A-P=3P-P=2P$

$\Rightarrow SI=\frac{PRT}{100}$

$\Rightarrow 2P=\frac{P\times R\times 16}{100}$

$\Rightarrow R=\frac{2P\times 100}{P\times 16}=12.5\%$