Find the sum on which the compound interest for 3 years at 10 % per annum amounts to rs.1655

Suppose the sum is Rs.P.
time; T = 3 years
Rate of interest;R = 10% p.a.
So amount accumulated after 3 years = $P{\left(1+\frac{R}{100}\right)}^T = P{\left(1+\frac{10}{100}\right)}^3$ = Rs.1655
$$\begin{gathered} \Rightarrow P{\left(\frac{11}{10}\right)}^3 = 1655 \\ \Rightarrow P\times \frac{1331}{1000} = 1655 \\ \Rightarrow P = \frac{1655\times 1000}{1331} = 1243.425 \end{gathered}$$
Therefore the required sum is Rs.1243.425