This is a brain teaser someone told me years ago.

A man who owns a radio store was waiting for his son to arrive so he could go and pay some bills at the post office, after his son had arrived he gave him strict instructions that if anyone came into the store wanting to buy anything that to let them know that he was only gone for five minutes and the father would help them when he returns and the son was not to sell anything while he was gone.

Just after dad left 3 people enter the store, they had just rented a flat and had $10.00 each to put in for a radio. After a minute or so the flat mates found a radio they like but it had no price on it, they asked the son how much it was. The son remember what his father told him but wanted to prove he was a good salesman, he looked at the radio and told the trio that it was $30.00, Perfect! they all pulled $10.00 out of their pockets and brought the radio and left.

The father returned just moments later and straight away noticed the radio was gone, he asked his son where the radio was and the son proudly told him about the sale. The father ask him how much he sold it for and the son replied $30.00, the father was furious as the radio was only $25.00 and didn't want people to think he was a ripoff, so he instructed the son to take $5.00 and chase after the flatmates to return the overcharge. The son left the store and noticed the customers down the street, as he was getting closer to them he realised he could not split $5.00 three ways so he decided to keep $2.00 for him self and give the flatmates $1.00 each which meant they only paid $9.00 each for the radio.

So in the end the Math should work like this

Each flatmate paid $9.00 for their share of the radio
The son kept $2.00
SO $9 x 3 = 27 + $2 = $29 where is the missing dollar.

Same here, Confused too.
I dont get how they worked it out. Good Braintesrer.

Thanks,
Mbd5882,
Asad Haider

They didn't pay $9.00. They paid $9 and 1/3. The error comes when you say that by giving each man $1, that their share is $9. That's mixing subtraction with division.

In keeping $2, the boy effectively lowers the price of the radio to $28.

Now supposing he gave the men $1.66 each, as was their due, they would only be missing a cent a cent at the end, on account of the repeating decimals.

I'm afraid my explanation wasn't the most lucid, but I lack the mathematical lexicon to describe such problems in-depth. I seem to recall Snopes writing about this, if you care to look through the archive.

No, I think it was pretty good

However, you could look at it in more than one way - especially with such "story problems", where how the problem is 'worded' can make a non-trivial difference to how you understand it. Obviously, the dollar cannot be missing, and most people realize that it's a trick of the language (i.e., the way the problem is phrased). You can find five distinct answers here:

A Math Forum Discussion

Should be interesting

Cheers!

I lokkes at the A Math Forum Discussion, and,
Ok, Theres no way i'm reading all that!No way.
Good brainteaser though. Really puzzlng.

Thanks,
Mbd5882,
Asad Haider

to easy and yes it is that you say that they eached payed 9 each wich is wrong so you just pretty much changed it without it being some thing like a teaser.

my rating: 1/5 for effort

No, the men did pay $9 each after the boy gave them each a dollar. The thing is, you aren't supposed to add the $2 that the boy took to the $27. You subtract.

Haha, that's a good one. I recall hearing it a very long time ago and being too confused to bother with it. But now I understand it more. It's neat how it works.

You could also look at it this way:

Each paid $10 for the "$30" radio.
It was only $25, so the guy takes $5 to give back.
He can't split $5 three ways even, so he keeps $2 and gives each guy $1.
That means each guy paid $9, x3 = $27. The guy gives them $1 each, x3.
$27 + $3 is $30, the original cost of the radio. So instead of $1 being missing, there is now $2 extra that the guy kept!

wow, I can't believe I didn't get that. I kept reading and re-reading not looking at the replies here to see if I could figure it out. but... that's a good one.

because essentially they paid $2 more than they should have for the radio b/c that's what the kid took.

very nice explanation Anndi