“A locomotive with a truck is travelling over a straight level line at the rate of 60 miles an hour. A man standing at the extreme rear of the truck casts a small stone into the air in a perpendicular direction. The stone travels upward at an average rate of 30 feet per second for 3 seconds; the height of the man’s hand from ground when the stone leaves is 15 feet. At what distance behind the train will the stone strike the ground in its descent?”
This logic puzzle game was invented by Israeli mathematician Gyora Benedek. The task is simple: Write a number in each blank square so that, in the finished diagram, a continuous chain of consecutive numbers connects the lowest number, 1, to the highest, 40. The numbers can connect horizontally, vertically, or diagonally. For example, the number 8 must go in the square above 7 because 7, 8, and 9 must occupy adjacent squares. Can you complete the rest of the diagram?
You’ve dealt about half the cards for a bridge game when you’re momentarily called away. When you return, no one can remember where you left off dealing. Without counting cards, how can you finish the deal accurately, so that each player receives the cards she’d have got if you hadn’t been interrupted?
A problem by Argentinian puzzlist Jaime Poniachik, from the February 1992 issue of Games magazine:
An ant crawls onto a clock face at the 6 mark just as the minute hand is passing 12. She begins crawling counterclockwise around the face’s circumference at a uniform speed. When the minute hand passes her, she reverses course and crawls clockwise without changing her speed. Forty-five minutes after her first encounter with the minute hand, it passes her a second time and she departs. How much time did she spend on the clock face?
54 minutes. Between the ant’s two encounters with the minute hand, the hand passed over 45 minute marks. In that time, the ant passed over 105 minute marks (45 minutes plus one complete circumference). The ratio of their speeds was thus 45/105, or 3/7. If x minutes elapsed before their first encounter, then in that time the minute hand advanced by x minutes while the ant crawled over 30 – x minute marks. So x/(30 – x) = 3/7, which gives x = 9 minutes, and the total time is 9 + 45 = 54 minutes.
UPDATE: I confused this in adapting it. The ant is crawling faster than the minute hand, not slower. She runs into the hand while crawling counterclockwise, reverses course, and then “laps” it, eventually crawling up behind it on the other side. The answer, 54 minutes, is correct, but my wording considerably confuses things. Thanks to everyone who alerted me to the error.
A joke chess problem by Bohuslav Sivák, from the Bratislavan newspaper Pravda, Dec. 29, 1972. White can mate in two moves by resorting to a drastic stratagem. What is it?
“Here you have the two to the ten of Diamonds, inclusive. Can you re-arrange them, still retaining the shape of the figure, so that the ‘pips’ total eighteen, across and down, in each line, and also diagonally from the corners?”
In What Is the Name of This Book? (1986), Raymond Smullyan describes two curious denizens of the Forest of Forgetfulness. The Lion lies on Mondays, Tuesdays, and Wednesdays, and the Unicorn lies on Thursdays, Fridays, and Saturdays. Each tells the truth on the days it doesn’t lie.
One day Alice encounters the two of them resting under a tree. They tell her:
Lion: Yesterday was one of my lying days.
Unicorn: Yesterday was one of my lying days too.
“From these two statements, Alice (who was a very bright girl) was able to deduce the day of the week. What day was it?”