You have to chase the Rupee!

Suppose you and me went to buy a gift for our friend's birthday. The shop's owner was not present at that time but there was one of his servants. We bought an article worth $Rs.50$ . We both paid $Rs.25$ each.

After sometime, the shop's owner came and told the servant that it was actually a $Rs.45$ article. He ordered the servant to return $Rs.5$ to us. On his way us he took $Rs.1$ and returned $Rs.4$ to us. We both shared it as $Rs.2$ each.

Now amount paid by each of us $= 25-2 = 23$

And total amount paid by us $= 23+23= 46$

If we add the money taken by the servant and which he returned us,

Then, total money $= 46+1+4 = \boxed{51}$

But wait a minute, from where had an extra $1 Rupee$ came ?