Simple interest on a certain sum at a certain annual rate of interest is 1/4 of the sum. If the numbers representing rate percent and time in years be equal, then the rate of interest is: Options:
A) 4 %.
B) 25/4 %.
C) 5 %
D) 6 %.
E) 3 %.
Explanation :   Let sum = x. Then, S.I. = x/4   Let rate = R% and time = R years.   [x * R * R / 100] = x / 4? R^2 = 100/4= 
<gadget id="calculator">100/4</gadget>
<output>25</output>
25   R= 5   Hence, rate of interest = 5 %.   Answer : 5 %
<result>C</result>
Simple interest on a certain sum at a certain annual rate of interest is 1/4 of the sum. If the numbers representing rate percent and time in years be equal, then the rate of interest is: