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 12 Choose the Next Letter Choose the next letter in the sequence: O T T F F S S ? Submitted by Ravi Doable 3.8 2 The Number Problem What does 3685=? 8809=6 7111=0 2172=0 6666=4 1111=0 3213=0 7662=2 8096=5 9312=1 4444=0 6824=3 9999=4 0345=1 2359=1 5522=0 9884=5 Enjoy, this is quite interesting. Submitted by Ravi Doable 4.0 2 The Bookworm Looking onto a shelf you see three books each labeled Volume 1, Volume 2, and Volume 3 respectively. Each book is 2.5 inches thick; that is the pages are 2 inches, and each cover .25 inches. A bo ... Submitted by Aakash Doable 5.3 5 Crazy Google Interview Question You are shrunk to the height of a nickel and your mass is proportionally reduced so as to maintain your original density. You are then thrown into an empty glass blender. The blades will start moving ... Submitted by Valentin Doable 6.0 10 Mutilated Chessboard Problem Suppose a standard 8×8 chessboard has two diagonally opposite corners removed, leaving 62 squares. Is it possible to place 31 dominoes of size 2×1 so as to cover all of these squares? Submitted by Ravi Hard 7.8 1 Greatest Area A farmer challenges an engineer, a physicist, and a mathematician to fence off the largest amount of area using the least amount of fence. The engineer made his fence in a circle and said it was th ... Submitted by Valentin Doable 5.0 12 Simple 24 Why is that if p is a prime number bigger than 3, then p^2-1 is always divisible by 24 with no remainder? Submitted by Aakash Doable 6.6 4 The Price Is Right Many shops have prices set just under a round figure, e.g. \$9.99 instead of \$10.00 or \$99.95 instead of \$100.00 . It is assumed that this is done because the price seems lower to the consumer. But th ... Submitted by Aakash Hard 7.0 2 Right or Left? This is interesting. Look at the animation below. Do you see the girl spinning clockwise or counter-clockwise Submitted by Valentin Easy 3.0 7 Cooking Time A cook must put a souffle exactly 9 minutes at the oven, but he only have a 7 minutes hourglass and a 4 minutes hourglass. How can he measure 9 minutes with those clocks? Submitted by Ravi Doable 5.7 1 Classic Knights & Knaves Raymond Smullyan has made a career of writing logic problems. His most famous have to do with a mythical island of Knights and Knaves. Knights always tell the truth, and Knaves always lie. As you a ... Submitted by Ravi Doable 5.5 28 12 Identical Balls You have 12 identical balls. One of them is slightly different in weight than the rest. You have three weighs of a balance scale to determine which ball is different and whether it is heavier or li ... Submitted by Valentin Doable 6.2 4 Up and Down Explain the following scenario: A man lives on the twelfth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets int ... Submitted by Valentin Hard 7.3 2 The Way Engineers Think A priest, a doctor, and an engineer were waiting one morning for a particularly slow group of golfers. Engineer: What’s with these guys? We must have been waiting for 15 minutes! Doctor: I don’t ... Submitted by Aakash Doable 6.0 2 Lockers A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony: There are one thousand lockers and one thousand students in the school. The princip ... Submitted by Aakash Hard 7.1