weirdest thing ever

courtesy: buddybits
i have never seen a thing weirder than this in my life!
have you? do you know how this works?
do comment to share your experience (its free:))

best aptitude question

3 boys go to the restaurant. Their bill was 75 rs
So they contributed 25 each. Manager then gives 5 rs back 
to the waiter and then waiter gave 3 rs back to them (1 to each) and 
put 2 rs into his pocket..
So their actual contribution is 24 because they got 1 rs 
back. so 24*3=72 and 2 rs into the waiter's pocket. so 
74+2=74
where is 1 rs?

Give your answer in comment and invite your friends to answer it! 

can you find the mistake?