Find the principal which yields a simple interest of Rs. 20 and compound interest of Rs. 21 in two years, at the same percent rate per annum?
Select the correct option:
A) Rs. 520  B) Rs. 480  C) Rs. 420  D) Rs. 200  E) Rs. 600
Explanation:   SI in 2 years = Rs. 20, SI in 1 year = Rs. 10   CI in 2 years = Rs. 21   % rate per annum = [(CI – SI) / (SI in 1 year)] *100   = [(21 – 20) / 20] * 100   = 5 % p.a.   Let the principal be Rs. X   Time = T = 2 years   % rate = 5% p.a.   SI = (PRT/100)   20 = (X*5*2) / 100   X = Rs. 200   ANSWER: Rs. 200
<result>D</result>
Find the principal which yields a simple interest of Rs. 20 and compound interest of Rs. 21 in two years, at the same percent rate per annum?