The forex rates are quoted in this manner INR/USD - 47.85/47.90. This means, the bank will buy one dollar for Rs 47.85 (bid/buy), and sell one dollar for 47.90 (ask/sell).
Similarly, to buy one dollar, the bank will give you .4040 DM (bid/buy) and take .4041 DM to sell 1 dollar (ask/sell).
The whole idea is that the currency seller would buy at a lower price and sell at a higher price and keep the difference as margin/profit.
Though your message doesn't specify, it is possible that you are looking for the cross rates. For that follow the following process:
You pay 47.90 to buy 1 USD. and Then you sell 1 USD to buy .4040 DM. So the cross rate INR/ DM is 47.90/.4040 or 118.5643
11 February 2013
generally per unit counted of denometer.... but you ahve to keep practical knowledge also.....sometimes we have take rates as per our g.k. which is market based rates.