Question

The compound interest on a certain money for 2 yr at the rate of 10% is 2100. Find the rate of interest in which amount will fetch the ssme interest in 2 yr time of the money is given in simple interest.

Answer 1

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Here is your answer
Let the sum is x
R = 10%
CI = 2100
T = 2 years = n= 2
As we know that
CI = P{(1+R/100)^n- 1}
$2100 = x((1 + \frac{10}{100}) {}^{2} - 1) \\ 2100 = x(( \frac{11}{10} ) {}^{2} - 1) \\ 2100 = x( \frac{121 - 100}{100} ) \\ x = \frac{2100 \times 100}{21} \\ x = 10000$
So Sum is Rs 10,000
SI = 2100
R = r%
T = 2 years

As we know that
SI = PRT/100
$2100 = \frac{10000 \times r \times 2}{100} \\ 2100 = 200r \\ r = \frac{2100}{200} \\ r = 10.5\%$

Therefore Rate of interest is 10.5%


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