A sum of money amounts to 9800 after 5 years and 12005 after 8 years at the same rate of simple interest. The rate of interest per annum is:  Choose the correct choice from the following:  A) 10  B) 18  C) 11  D) 12  E) 15
D   12   S.I. for 3 years = (12005 - 9800)= 
<gadget id="calculator">(12005 - 9800)</gadget>
<output>2_205</output>
2205.   S.I. for 5 years= (2205/3)x 5 = 3675   Principal = (9800 - 3675)= 
<gadget id="calculator">(9800 - 3675)</gadget>
<output>6_125</output>
6125.   Hence, rate= (100 x 3675)/(6125x5)% = 12%
<result>D</result>
A sum of money amounts to 9800 after 5 years and 12005 after 8 years at the same rate of simple interest. The rate of interest per annum is: