The interest charged on a certain sum is Rs.720 for one year and Rs. 1,497.60 for two years. Find whether the interest is simple or compound. Also calculate the rate $%$ and the sum.

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Solution

Let P the the sum
Let - r " interest
Case I S. J.
$\begin{matrix} S I f o r y e a r = \frac{P r}{100} S I f o r y e a r = \frac{2 p r}{100} \end{matrix} ⎫ ⎬ ⎭ \Rightarrow S I_{2} = 25 I_{1} B u t I_{2} = 1497.60 & I_{1} = 720 ∴ I_{2} \neq 2 I_{1} \Rightarrow T h i s i s n o t S I C I . C / I = P (1 + \frac{r}{100}) - P = 720 = P [/ 1 + \frac{r}{100} - / 1] = 720 \frac{P r}{100} = 720 \Rightarrow P r = 72000$
Interest for $2^{n d} = C I_{2} - C S_{1} = 1497.26 - 720 = 7.77.26$
$∴ 720 C I_{1}$ has become $777.26 C I_{2}$
$∴ r = \frac{777.26 - 720}{720} \times 100 = \frac{57.26}{720} \times 100 ≅ 7.95 % ∴ P = \frac{72000}{r} = \frac{72000}{7.95} \times = R s 9053.53$

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The interest charged on a certain sum is Rs.720 for one year and Rs. 1,497.60 for two years. Find whether the interest is simple or compound. Also calculate the rate% and the sum.

The interest charged on a certain sum is Rs.720 for one year and Rs. 1,497.60 for two years. Find whether the interest is simple or compound. Also calculate the rate $%$ and the sum.