


46. A four years NSC certificate was purchased for $₹500$ with $₹1000$ being the maturity value. Find the rate of simple interest. | |
A. $16\%$ | B. $24\%$ |
C. $22\%$ | D. $25\%$ |
Discuss |
Answer: Option D
Explanation:
P $=500$
T $=4$
SI $=1000-500=500$
$\text{R}=\dfrac{100×500}{500×4}=25$
47. If simple interest on a certain sum of money for $8$ years at $4\%$ per annum is same as the simple interest on $₹560$ for $8$ years at the rate of $12\%$ per annum then the sum of money is | |
A. $₹1680$ | B. $₹1820$ |
C. $₹1040$ | D. $₹1120$ |
Discuss |
Answer: Option A
Explanation:
Let the sum of money be $x$
$\dfrac{x×4×8}{100 }=\dfrac{560×12×8}{100 }\\\Rightarrow x×4×8=560×12×8\\\Rightarrow x×4=560×12\\\Rightarrow x=560×3=1680$
simple interest on $₹560$ for $8$ years at $12\%$
$=\dfrac{560×12×8}{100}=537.6$
That is, simple interest on the required sum for $8$ years at $4\%$ is $537.6$
Required sum $=\dfrac{100×537.6}{4×8}=1680$
Let the sum of money be $x$
SI $\propto$ PR (because T is constant here)
Therefore, $4x=560×12$
$\Rightarrow x=1680$
48. If a sum of money trebles itself in $40$ years, what is the rate of interest? | |
A. $4\%$ | B. $5\%$ |
C. None of these | D. $6\%$ |
Discuss |
Answer: Option B
Explanation:
Let the sum of money be $x$
$x$ becomes $3x$ in $40$ years.
Simple interest $=3x-x=2x$
R $=\dfrac{100×2x}{x×40}=5$
Refer formula
R $=\dfrac{100(3-1)}{40}=5$