Catogiries

What's HOT

Cards with cross



      You have a stack of 23 cards. Each card has an image of a cross on one side 
& an image of a circle on the other side. You know that 14 cards in the stack are 
lying with the cross up, and therefore 9 cards are with the circle up. However,
you do not know in which order the cards are. Moreover, you are in completely dark 
room,so you cannot see anything. 



The Question: How can you, without seeing anything, divide the stack of 
cards in two smaller stacks, in such a way that both stacks have the same 
number of cards with a cross up?


A Hint : You can turn cards round


The Answer: 
Take 14 cards from the stack. Of these 14 cards, k cards are with the cross up 
and therefore 14-k cards are with the circle up. In the remaining stack of 9 
cards are 14-k cards with a cross up.
                                      Then turn the stack of 14 cards round. 
Now there are 14-k cards with a cross up in both stacks.Note that we do not 
know exactly how many cards are lying with a cross up in both stacks (or how
many cards are lying with a circle up). We only know that both stacks have 
the same number of cards with a cross up.

Tag : , ,

What's that number? ;)


View Answer & Explanation

Answer
:
6
Explanation
:
Looking at the diagram in rows, the central circle equals half the sum of the numbers in the other circles to the left and right of the centre.


Tag : , ,

- Copyright © Teen Duniya - Skyblue - Powered by Blogger - Designed by Johanes Djogan -