The compound interest on a certain sum for 2 years at 10% per annum is Rs. 1155. The simple interest on the same sum for double the time at half the rate percent per annum is ?

Let the sum be Rs.x. Then, 

  $x1+\frac{10}{100}2-x=1155$

$\Rightarrow x\frac{11}{10}2-1=1155$

=> x =5500

sum = Rs. 5500.

So, S.I = Rs.  $\frac{5500\times 5\times 4}{100}$ = 1100