Interview Question - The Waiter

[kp7796]

Three men in a cafe order a meal the total cost of which is $15. They each contribute $5. The waiter takes the money to the chef who recognizes the three as friends and asks the waiter to return $5 to the men.

The waiter is not only poor at mathematics but dishonest and instead of going to the trouble of splitting the $5 between the three he simply gives them $1 each and pockets the remaining $2 for himself.

Now, each of the men effectively paid $4, the total paid is therefore $12. Add the $2 in the waiters pocket and this comes to $14.....where has the other $1 gone from the original $15?

[MrMancunian]

The $1 doesn't exist.

When the waiter returns the $3 to the three men, they all paid $4, which makes $12. The chef has $10 in his pocket and the waiter has $2 in his pocket.

Look at it like this. The men each contribute $5, which is 3 x -5 = -15. The waiter returns each man $1, which is 3 x 1 = 3. The chef keep $10, and the waiter keeps $2.

-5 'is taken from man 1
-5 'is taken from man 2
-5 'is taken from man 3
+10 'is given to the chef
+2 'is taken by the waiter
+1 'is given to man 1
+1 'is given to man 2
+1 'is given to man 3
--------
0

See? ;-)