Mukesh borrowed a sum of Rs. 10000 at simple interest from a bank. After two years he takes Rs. 12000 more as loan and discharge all the debt at the end of next 3 years depositing Rs. 27160 to the bank. What is the rate of interest per annum?
Choose one:
A) 5 %
B) 6 %
C) 8 %
D) 10 %
E) none of these

Rationale: si = 27160 - ( principal amount ) = 27160 - 22000 = 5160 . now , ( 10000 * 5 * r / 100 ) + ( 12000 * 3 * r / 100 ) = 5160 . 500 r + 360 r = 5160 . . . . . rate = 6 % . answer : b
Answer: B