At what simple rate of interest a sum is double in 8 years ?

Correct option is B

1. Substitute the known values

   Simple Interest (SI) = (Principal x Rate x Time) / 100
2. Let the principal amount be 'P'.

Time (T) = 8 years

Simple Interest (SI) = P (since the sum doubles)

P = (P * R * 8) / 100

1 = (R * 8) / 100

R = 100 / 8
R = 12.5%