The most popular answer for this teaser is ‘today’. Of course this only works if you’re reading it on that particular date or if the date is not specified. Another option is to respond literally with ‘a date’. Lastly, certain dates could be squeezed into letters using Roman numerals if you abbreviate the year to 2 numerals. For example, January 20th, 2011 would be I XX XI.
She will always need to give you 5 apples. You both need at least 5 apples to begin with, but apart from that it doesn’t matter exactly how many you each have. When she gives you 5 you will have 10 more than her because she will lose 5 and you will gain 5, resulting in a net difference of 10.
For example, if you each have 25 apples and she gives you 5 of hers, she will be left with 20 and you will now have 30, precisely 10 more than she has.
In 2012 a class was divided into 2 groups. Their assignment was to find the names of at least 3 children who were born on the same day from 5 different months of 2011. These were the results:
Group 1
August 20: Oliver, William, and Adam.
January 3: John, Alice, and Ken.
September 7: Bruce, Shane, and Peter.
June 11: April, Patrick, and Bobby.
July 19: Trent, Julie, and Charles.
Group 2
March 1: Karl, Willie, and Patty.
February 29: Blake, Kobe, and Wayne.
December 24: Kyle, Chad, and Zoe.
May 12: Matthew, Manny, and Adrian.
November 20: Greg, Fiona, and Elizabeth.
The members of group 2 got an F on the assignment. Why?
A similar problem can be found in L.A. Graham’s Ingenious Mathematical Problems and Methods with a range of 1 to 9, but the principle remains the same – the numbers with the smallest difference produce the largest product. You start out with the highest two digits, 7 and 6, then attach 5 and 4, putting the smaller of the two digits with the larger number, giving you 74 and 65. The next two highest digits are 3 and 2, giving you 742 and 653. Finally, you add the 1 to the lower number. Page 80 has the details of that solution.
A man wants to get into a night club where the bouncers test each person before they can enter. The man waits and watches.
A woman walks up to the bouncers and the bouncers say 6. The woman replies with 3 and goes in.
A small man walks up and they say 12. The man replies 6 and is admitted.
The first guy thinks he’s figured it out and walks up. They say 4 and the man replies with 2, but they don’t let him in.
Phil asks his friend Stan when his birthday is. Stan replies that he was 32 the day before yesterday and next year he’ll be 35. When is his birthday and how is this possible?
Today is Jan 1st and his birthday is on December 31st. He was 32, then turned 33 on Dec 31st, and this year on Dec 31st he’ll turn 34, so next year he’ll be 35.