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. What is the time?  Choose the correct choice from the following choices:
A) 5 months  B) 6 months  C) 7 months  D) 8 months  E) 4 months
Bankers Discount, BD = Simple Interest on the face value of the bill for unexpired time.   True Discount, TD = Simple Interest on the present value for unexpired time.   Simple Interest on Rs. 1600 = True Discount on Rs.1680   =&gt; Rs. 1600 is the Present Worth (PW) of Rs. 1680   =&gt; Rs. 80 is the Simple Interest of Rs.1600 at 15%   ⇒80=(1600×T×15)/100   ⇒80=16×T×15   ⇒5=T×15   ⇒1=T×3   ⇒T=1/3 year   =12/3= 
<gadget id="calculator">12/3</gadget>
<output>4</output>
4 months   ANSW4 monthsR:4 months
<result>E</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. What is the time?