Question

If a certain sum of money at si doubles itself in 5 yrs then what is d rate? 5% 20% 25% 14.8%

Answer 1

$\mathfrak{Answer:}$

= 20%.

$\mathfrak{Step-by-Step\;Explanation:}$

$\underline{\bold{Given\;in\;the\;Question:}}$

• A sum becomes 2 times.
• Time = 5 years.

$\mathbb{SOLUTION:}$

Let the principle be Rs. x.

So amount = Rs. 2x.

$\bigstar\quad\textsf{We know that : \boxed{\bold{Simple\;Interest=Amount-Principle.}}}\\\\\\\tt{=2x-x}\\\\\\\tt{=Rs.x.}$

$\bold{Also:}\\\\\\\boxed{\bold{SI=\dfrac{Principle\times Time\times Rate}{100}}}\\\\\\\mathfrak{According\;to\;Question:}\\\\\\\implies\tt{x=\dfrac{x\times 5\times r}{100}}\\\\\\\implies\tt{100x=5xr}\\\\\\\implies\tt{r=\dfrac{100x}{5x}}\\\\\\\implies\tt{r=20\%.}\\\\\\\\\boxed{\boxed{\bold{Rate=20\%.}}}$