The banker’s discount on Rs. 1600 at 15% per annum is the same as true discount on Rs. 1680 for the same time and at the same rate. The time is :  Choices:
A) 2 months
B) 4 months
C) 6 months
D) 7 months
E) None
Sol.   S.I. on Rs. 1600 = R.D. on Rs. 1680.   ∴ Rs. 1600 is the P.W. of Rs. 1680, i.e., Rs. 80 is S.I. on Rs. 1600 at 15%.   ∴ Time = [100 * 80 / 1600 * 15] year = 1/3 year = 4 months.   Answer 4 months
<result>B</result>
The banker’s discount on Rs. 1600 at 15% per annum is the same as true discount on Rs. 1680 for the same time and at the same rate. The time is :