Monday, January 16, 2017

Five Card Trick


A mathematician asks a volunteer to give him five cards drawn from a pack of fifty-two. He hands one card back to the volunteer and arranges the remaining four in some sequence he chooses. He then hands the sequence to a second volunteer and leaves the room. His assistant enters. The assistant asks the second volunteer to read out aloud the sequence handed to him. The assistant ponders a little and correctly announces the identity of the card held by the first volunteer. How could this be done? In general, how large a deck of cards can be handled if n cards are drawn initially?


Solution: Click here for the solution!


Thursday, January 12, 2017

X and Y

Two numbers are such that if the first gets 24 from the second they will be in the ratio 2 to 1, but if the second receives 33 from the first, their ratio will be 1 to 5. What are these two numbers?




Answer: 52 and 62


What are the four numbers?

The sums of four numbers, omitting each of the numbers in turn, are 27, 23, 21 and 19. What are the four numbers?



Answer: 3, 7, 9, and 11
7 + 9 + 11 = 27
3 + 9 + 11 = 23
3 + 7 + 11 = 21
3 + 7 + 9 = 19

Replace the question mark!

Which of the boxes should be used to replace the question mark?





Answer: A










Sunday, October 2, 2016

Sander Parallelogram

Sander Parallelogram 

Sander Parallelogram - The Sander illusion or Sander's parallelogram is an optical illusion described by the German psychologist Friedrich Sander (1889–1971) in 1926. However, it had been published earlier by Matthew Luckiesh in his 1922 book Visual Illusions: Their Causes, Characteristics, and Applications.
Sander Parallelogram

Note:The two lines in purple have the same length; Sander's Parallelogram, also known as "Sander Illusion" is an optical illusion described by the German psychologist Friedrich Sander.