Correct Answer: INR 11,893

Solution : Amount after 6 years = INR 53,520
Amount after 3 years = INR 35,680
Principal for next 3 years = INR 35,680
Principal = $P$
We know that,
$ A= P(1+\frac{R}{100})^{T}$, Where $A$ is the total amount, $P$ is the principal amount, $R$ is the rate of interest per annum, and $T$ is the time in years.
For 1st case:
$35680= P(1+\frac{R}{100})^{3}$
⇒ $\frac{35680}{P}= (1+\frac{R}{100})^{3}$............................(1)
For 2nd case:
⇒ $ 53520= 35680(1+\frac{R}{100})^{3}$
⇒ $ \frac{53520}{35680}=(1+\frac{R}{100})^{3}$............................(2)
From equation 1 and 2, we get:
⇒ $\frac{35680}{P}= \frac{53520}{35680}$
⇒ $P= \frac{35680\times35680}{53520}$
⇒ $P$ = INR 23,786.66
Compound interest for first 3 years = 35,680 – 23,786.66 = 11,893.34 = 11,893 (nearest integer)
Hence, the correct answer is INR 11,893.