LOGIC AN OPEN-AND-SHUT CASE
A giant gymnasium contains a row of 1,000 lockers, all closed, and a line of 1,000 people.
The first person runs along and opens every locker.
The second person then runs along and closes every second locker, starting with locker #2.
The third person runs along and changes the status of every third locker (if it is open they shut it, and if it is shut they open it), starting with locker #3.
The fourth person runs along and changes the status of every fourth locker, starting with #4, and so on until all of the people have passed by all of the lockers.
Which lockers are open in the end?
—FRED BERNARD
LOGIC CHRISTMAS EXCHANGE
Four couples, the Fletchers, the Greens, the Hills, and the Kings, all related to each other, gathered for a gift exchange. Each person gave a gift to one person and received a gift from one other person, selected
