Toll Bridge Trouble–a math puzzle (answer included)
An old man lived in a little hut by a bridge which crossed a deep river.
One day a wicked water-spirit appeared to him and said: “My friend, I know you are very poor. Now I will increase whatever money you may have twofold, asking only in return this small favor, that every time you cross the bridge you will throw twenty-four cents into the water, and at the same time the money you have left shall be doubled.” The poor old man was delighted at what he thought a generous offer of the water-spirit, and faithfully fulfilled all the conditions; but, to his sorrow and astonishment, when he had three times thrown the tribute of twenty-four cents to the water-spirit, he found himself penniless.
How much money did he have when the water-spirit first appeared to him?
ANSWER BELOW
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[The answer is 42 cents. A better question is, why, when he had only 24 cents left, did he cross the bridge the third time? Of course, if he were that smart he wouldn’t have entered into the deal in the first place.
Now, if he had started with 48 cents, he could cross indefinately, but wouldn’t have increased his wealth. Not a great deal, but it’s better than you get on the George Washington Bridge. Obviously, if he started out with 49 cents or more, it would be a winning deal. As a matter of fact, at 49 cents, it would take only 10 trips to make over $10. So if any wicked water-spirits try to make such a deal with you, report him to the Port Authority, or at least make sure you have at least one penny more than double the tribute he demands.]
Tags:bridge,math,money,puzzle,riddle,toll,troll
