An investor invested two equal sums of money for 1 year. The first sum was invested at the rate of R% annual rate of interest and the interest compounding was half-yearly. The second sum was invested at the rate of r% annual rate of interest and the interest compounding was quarterly. If at the end of the year, the amounts he received are equal, what is the value of R in terms of r?
Q. An investor invested two equal sums of money for 1 year. The first sum was invested at the rate of R% annual rate of interest and the interest compounding was half-yearly. The second sum was invested at the rate of r% annual rate of interest and the interest compounding was quarterly. If at the end of the year, the amounts he received are equal, what is the value of R in terms of r?
Denote Principal Amount: Let's denote the principal amount for each investment as P. For the first sum with half-yearly compounding, the amount A1 after 1 year at R% interest rate is calculated using the formula for compound interest: A1=P(1+200R)2.
Calculate Amount A1: For the second sum with quarterly compounding, the amount A2 after 1 year at r% interest rate is calculated using the formula for compound interest: A2=P(1+400r)4.
Calculate Amount A2: Since the amounts received from both investments are equal at the end of the year, we can set A1 equal to A2: P(1+200R)2=P(1+400r)4.
Set Amounts Equal: We can cancel out the principal P from both sides since it's the same for both investments: (1+200R)2=(1+400r)4.
Take Square Root: Now, let's take the square root of both sides to simplify the equation: 1+200R=(1+400r)2.
Expand Right Side: Expanding the right side using the binomial theorem gives us: 1+200R=1+2(400r)+(400r)2.
Isolate Terms: Subtract 1 from both sides to isolate the terms with R and r: $\frac{R}{\(200\)} = \(2\)\left(\frac{r}{\(400\)}\right) + \left(\frac{r}{\(400\)}\right)^\(2\).
Simplify Right Side: Simplify the right side by combining like terms: \(\frac{R}{200} = \frac{r}{200} + \left(\frac{r}{400}\right)^2\).
Multiply by \(200\): Now, let's multiply through by \(200\) to solve for \(R\): \(R = r + 200\left(\frac{r}{400}\right)^2\).
Simplify Second Term: Simplify the second term on the right side: \(R = r + \frac{r^2}{8}\).
Find Value of R: So, the value of R in terms of r is: \(R = r + \frac{r^2}{8}\).
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