## Thursday, November 12, 2009

### The Case of a Missing Dollar

You buy \$60 worth of products at the store and give the cashier 3 x \$20. The cashier is scanning your store loyalty card and congratulates you on receiving \$5 off from your purchase. She then asks whether you would like to contribute to a local charity. You agree to give \$2, and then she gives you the remaining \$3 back.
So, overall you paid \$60 - \$3 = \$57
There are also \$2 you gave to the charity. \$57 and \$2 are \$59 total.
But you started with \$60, where is the additional dollar?

Submit your answer on our Family Puzzle Marathon site. Solve three puzzles and get a prize!

Wang said...

I like this puzzle.

The additional dollar is not missing, it's just that the problem is that money is added up strangely.

You gave \$57 and you should be adding \$3 because that is what you got back in change - not what you gave to charity.

If for instance, you bought \$55 of stuff and then gave \$4 in charity then the question would ask

Overall you paid \$60 - \$1 = \$59, but then you gave \$4 in charity so you actually paid \$63 !!!! Where did the extra \$3 come from?

Maria said...

You got the trick!
First puzzle for W, who also made a very sophisticated comment on a birthday cake puzzle.

New one tomorrow!

kj said...

It is unclear whether the \$55 price includes the \$5 discount or not. This does not change the answer.

You give \$60 for a \$55 purchase, and should receive \$5 change. You donate \$2 of the change, and so receive \$3 from the cashier.

Here is the mistake:
There are also \$2 you gave to the
charity. \$57 and \$2 are \$59 total.

You have added the \$2 donation to the wrong number. You should instead say "\$55 and \$2 are \$57 total" as in order to find how much you spent you add the purchase price and the donation.

Maria said...

Thank you for the good clarification, Kimberly.

rubix journal said...

now i got confused :)

Maria said...

You entered the store with \$60, left there \$57 and still have \$3 in your wallet.
60=57+3

From the \$57 you left at the store, \$55 goes for the items you purchased and \$2 to the charity.
57=55+2

The puzzle tries to confuse you to add \$2 to \$57 again.

Anonymous said...

The dollar was always there. The addition they gave was wrong. First add \$2 to the \$60. Subtract \$5 then add \$3. You get \$60