A sum of money becomes Rs. 2200 after three years and Rs. 4400 after six years on compound interest. The sum is  Pick:
A) Rs. 1400 B) Rs. 1100 C) Rs. 1000 D) Rs. 1200 E) Rs. 1400
Explanation:   Let the sum be P and rate of interest be R% per annum.   Amount after 3 years = 2200   P(1 + R/100)T = 2200   P(1 + R/100)3 = 2200 --- ( 1)   Amount after 6 years = 4400   P(1+R/100)T = 4400   P(1 + R/100)6 = 4400 --- (2)   (2) ÷ (1) =&gt; [P(1+R/100)6]/[P(1+R/100)3] = 4400/2200= 
<gadget id="calculator">4400/2200</gadget>
<output>2</output>
2=&gt; (1+R/100)3 = 2 (Substituting this value in equation 1)   =&gt; P × 2 = 2200   P = 22002 = 1100   Answer: Option Rs. 1100
<result>B</result>
A sum of money becomes Rs. 2200 after three years and Rs. 4400 after six years on compound interest. The sum is