Monday, June 23, 2008

Numbers don't lie?

So you think numbers don't lie? Give this mind teaser a try:

Three men go to dine together in a restaurant. The bill comes to $25 and they each contribute $10. The waiter takes the money to the cashier, who gives the waiter the $5 in change. Being a non-assuming waiter he takes the change back to the three men. The men take back a dollar each, hence effectively paying $9.00 each, and they leave the $2.00 as a tip for the waiter. On their way out, one of them points out that they each paid $9.00 for the meal, amounting to $27.00, and the waiter was left with $2.00. What happened to the other remaining dollar? Did the cashier pocket it?


This is a famous puzzle which supposedly first appeared in R. M. Abraham’s Diversions and Pastimes in 1933. Don't be disheartened if you can't figure it out. Many don't. I am not going to spoil your fun by revealing the answer yet.

I am very interested to know how many and who is able to solve the puzzle. I would appreciate if you can participate in the poll that I set up.

Yes, numbers indeed don't lie. But it is exceedingly easy to mislead, confuse, lie, deceive and manipulate with numbers.

While the whole country is focused on Petronas' account, perhaps we were intentionally being mislead into looking at the wrong thing?

More to come ...

(see The fallibility of the human brain for explanation)

5 comments:

Humble Voice said...

I presented this puzzle to an accountant friend of mine. This was her line of reasonings:

No, they paid $28 right - because the waiter took $2.... eh... $28 divide by 3 is $7.33 .... hang on ... er .... oh yes - $25 plus $3 equals $28, is that right?

Well, I thought accountants are good with numbers...

trekker said...

Hahaha... This is a big joke. Same goes for the Petronas accounts.

antu said...

the reason people can't solve this puzzle is because people tend to look at face value - in this case they focus on the question raised by the friend outside the restaurant instead of the numbers. Numbers don't lie, that's right if you put them all on the table:

25+3+2 = 30

antu said...

forgot to type

30-25-1-1-1=2

27-25=2


2 goes to waiter

Anonymous said...

The $3 has already been pocketed by the three guys so all we're only left with is only $27 to be taken into account..

So we can't add another non-existing $2 into the $27 anymore right?

Simple as that... ($9 * 3)- $2 = $25

I guess only someone like Pak Lah could "convince" people that the $2 really does exist..