errors

Every author has to face the fact that sometimes he gets things wrong. This is chastening when you realize it yourself but doubly so when pointed out by schoolchildren from the other side of the world who write to you in their best handwriting.  Here are some errors from my books:
Lateral Thinking Puzzlers:

Page 26 4.4

The Woman on the Bridge II

In South America a woman was being chased by a gang of bandits. She had escaped with two solid gold balls and the bandits wanted to kill her and take the balls. She came to a wooden bridge over a deep ravine. The bridge was 100 feet long. There was a notice on the bridge that said ‘Maximum weight on this bridge 112 pounds.’ Strangely enough this notice was 100% accurate – the bridge would break if it carried more than 112 pounds. She weighed 100 pounds and each of the balls weighed 10 pounds. There was no time to leave one ball behind and come back for it later. And yet she managed to escape across the bridge with both balls. How could this be so?

Answer given in the book

She juggled the balls as she went over the bridge.

Comment

It has been pointed out by physicists with more degrees than a protractor that this does not work. Although you can juggle so that you have no more than one ball in your hands at any one time the average downward force on the bridge will still be 120 pounds and at times it will be higher. As you throw a ball upwards an additional downward reaction force is exerted on the bridge to match the force required to accelerate the ball out of your hand.

So the answer I give now is: She rolled one ball over the bridge before running over with the second ball. Far-fetched I grant you but it is possible (especially if the bridge has sides and a slight downward incline) and it does not break the laws of physics.

Great Lateral Thinking Puzzles

Page 8 1.14

Pond Problem

A man wishes to reach in island in the middle of a square ornamental lake without getting wet. The island is 20 feet from each edge of the pond and he has two planks each 17 feet long. How does he get across?

Answer given in the book:

He lays one plank across the corner and the other from the centre of the first plank to the island.

Comment

I am embarrassed to say that this just does not work. Fortunately most people do not check the mathematics. The diagonal distance from the corner to the island is 20 times the square root of 2 = 28.284 feet. The distance from the middle of the triangle formed at the corner to the corner is 8.5 feet. So this plus 17 feet is insufficient to bridge the diagonal. The two planks need to be at least 18.9 feet long for this solution to work.

Perplexing Lateral Thinking Puzzles

Page 12

February 1866

What happened in February 1866 that will not happen again for another two and a half million years?

Answer given in the book:

There was no full moon. January and March of that year both had two full moons and February none – a most unusual occurrence.

Comment

It appears that the same thing happened in 1999. So what is all the fuss about?  We were out by 2499887 years, sorry.

 

Brain-Busting Lateral Thinking Puzzles

Page 54

The Great Wall

An American, who had never been to any country other than the United States, was standing on solid ground one day when he saw the great wall of China with his own eyes.  How come?

Answer given in the book:

He was an astronaut standing on the moon – from where the great wall of China is visible.

Comment

Oh no it is not.  It is a popular but incorrect belief that the great wall of China is visible from the moon.  “The only thing you can see from the Moon is a beautiful sphere, mostly white, some blue and patches of yellow, and every once in a while some green vegetation,” said Alan Bean, Apollo 12 astronaut. “No man-made object is visible at this scale.”
If you spot other errors in the books then be sure to email me your comments – but please go easy on my bruised ego!