Find the principal if the interest compounded at the rate of 10% per annum for two years is Rs. 420 ?

Given,
Compound rate, R = 10% per annum
Time = 2 years
C.I = Rs. 420
Let P be the required principal.
A = (P+C.I)
Amount, A =  $P1 + \frac{r}{100}n$

(P+C.I) =  $P1 + \frac{10}{100}2$

(P+420) = P[11/10][11/10]

P-1.21P = -420

0.21P = 420

Hence, P = 420/0.21 = Rs. 2000