The simple interest on a certain sum of money for 2 l/2 years at 12% per
annum is Rs. 40 less tban the simple interest on the same sum for 3 ½ years at 10% per annum. Find the sum.  Choose the most appropriate option:
A) Rs. 700.
B) Rs. 200.
C) Rs. 600.
D) Rs. 800.
E) Rs. 400.
Let the sum be Rs. x   Then, ((x*10*7)/(100*2)) – ( (x*12*5)/(100*2)) = 40   (7x/20)-(3x/10)=40   x = (40 * 20)= 
<gadget id="calculator">(40 * 20)</gadget>
<output>800</output>
800.   Hence, the sum is Rs. 800.   Answer is Rs. 800..
<result>D</result>
The simple interest on a certain sum of money for 2 l/2 years at 12% per
annum is Rs. 40 less tban the simple interest on the same sum for 3 ½ years at 10% per annum. Find the sum.