Interests

Puzzles

• You and your colleague C know that your boss A’s birthday is one of these ten dates: March 4, March 5, March 8, June 4, June 7, September 1, September 5, December 1, December 2, or December 8. A tells you only the month of his birthday and tells C only the day. You first say, “I don’t know A’s birthday; C doesn’t know it either.” After hearing this, C replies, “I didn’t know A’s birthday, but now I know it.” You then say, “Now I know it, too.” After looking at the ten dates and hearing the exchange, your administrative assistant writes down A’s birthday without asking any questions. What date did the assistant write?
• You split 1,000 coins into two nonempty piles containing x and y coins and add x × y to a running sum. You then split each resulting pile into two nonempty piles; whenever a pile is split into piles of sizes a and b, add a × b to the running sum. Continue recursively until every pile contains exactly one coin, without adding the final singleton piles themselves to the sum. What is the final sum, and how can you prove that it is the same no matter how the piles are divided?
• A blind man has four pills: two red and two blue. The pills are identical in shape, size, texture, weight, smell, and every other property except color, so he cannot distinguish them. He must consume exactly one red pill and one blue pill; consuming two of the same color will kill him. What strategy ensures that he takes exactly one pill of each color?
• How can you measure exactly 45 minutes using two identical wires and matches if each wire takes exactly one hour to burn but burns at a nonuniform rate? For example, the two halves of a wire might burn in 10 minutes and 50 minutes, respectively.
• Why is a manhole cover round? Aside from a circle, what other shape could work?
• One of 12 coins is counterfeit and is either heavier or lighter than the rest. Can you identify the counterfeit coin and determine whether it is heavier or lighter using only three weighings on a beam balance?
• Two urns initially contain one ball each. Each of the remaining n − 2 balls is placed into an urn with probability proportional to the number of balls already in that urn. What is the expected number of balls in the urn that ends with fewer balls?
• A guard watches 100 perfectly rational prisoners in a field. The prisoners are numbered 1 through 100, everyone knows every prisoner’s number, and the guard has a gun with exactly one bullet. Each prisoner will try to escape if they believe they have any chance of surviving, but will stay if they are certain the guard will shoot them. Everyone trusts the guard to follow any rule he announces, and the guard never misses. What rule can the guard announce that guarantees no prisoner tries to escape?
• A traveler must take a tiger, a sheep, and a bag of wheat across a river in a boat that can carry only the traveler and one item. The tiger cannot be left alone with the sheep, and the sheep cannot be left alone with the wheat. How can the traveler get everything across safely?
• A car is hidden behind one of three doors, with goats behind the other two. After you choose a door, a host who knows what is behind every door always opens a different door to reveal a goat and always offers you the chance to switch to the remaining unopened door. Should you switch, stay, or does it make no difference?
• An Angel and a Devil play on an infinite grid. On each turn, the power-1 Angel moves to any unblocked square one king-step away, while the Devil blocks any one unoccupied square anywhere on the grid. The Angel may never land on a blocked square, and the Devil wins by trapping the Angel. Can the Angel evade the Devil forever?
• Prisoners A, B, and C are told that exactly one of them will be pardoned, chosen uniformly at random, and the other two will be executed. A asks the guard to name one of B or C who will be executed. The guard must answer truthfully and, if both B and C will be executed, chooses which name to give by a fair coin toss. The guard says B. What are A’s and C’s probabilities of being pardoned after hearing this?

Some more fun puzzles can be found here, here, here, and here.

Films

• 3 Idiots (2009)
• Fight Club (1999)
• Coach Carter (2005)
• The Green Mile (1999)
• Dead Poets Society (1989)
• Good Will Hunting (1997)
• 10 Things I Hate About You (1999)
• Chennai Express (2013)
• Taare Zameen Par (2007)
• PK (2014)

Experiences

• womblike gals submits
• robots honestly entrust
• birdcage aside clapped
• surpassing official arranger
• candid crouched indicate
• shifters strides buttery
• trouser model clarifies
• cerebrum doing miss

Books

• 1984 (George Orwell)
• Sherlock Holmes (Arthur Conan Doyle)
• Animal Farm (George Orwell)
• Don Quixote (Miguel de Cervantes)
• Ender’s Game (Orson Scott Card)

Songs

• Mary Jane’s Last Dance (Tom Petty and the Heartbreakers)
• All That She Wants (Ace of Base)
• Knockin’ on Heaven’s Door (Bob Dylan)
• Mere Rashke Qamar (Nusrat Fateh Ali Khan)
• Tere Mast Mast Do Nain (Rahat Fateh Ali Khan and Shreya Ghoshal)
• Nour El Ein (Amr Diab)
• Sitting, Waiting, Wishing (Jack Johnson)
• Rodeo Clowns (Jack Johnson)

And taking photos.