Where did two dollars go?? One of my school friends gave me this sum.Its basically a story formated into a sum
STORY
There were 3 friends.
They each gave 20 dollars to buy a radio.
They bought the radio for 60 dollar.
Later the shopkeeper saw that the cost of the radio was 50 dollar.
So he went to the friends to return 10 dollar.
On the way (of returning) he thought that 10 dollar can't be divided among 3 friends.
So he himself took 4 dollar  and rest 6 dollar was divided among three friends. 
thus each friend got 2 dollar.
SUM
Initially the shop keeper had 60 dollar.
And each friend finally gave 18*3=54 dollars
and the shopkeeper himself took 4 dollar.
thus total 58 dollar.
THEN WHERE DID EXTRA  2 DOLLAR GO?????
I tried it in many ways but still could not.
can any one help me out.

No you have interpreted wrongly see the shopkeeper has total $54$ dollars not $58$ so $54+2(each)=60$ each got $2$ again. What you have done is radio costs $54$ and top of that shopkeeper takes $4$ dollars which is wrong so two dollars went nowhere 
