Repost: Brain Teasers

Q.1 There are 10 coin making machines. 9 out of them make coins weighing 1 gm each. One (unknown) machine is faulty and makes coins 100 mg heavier.... Click for details
Q.2 This one's not for kids. There are 12 coins. One of them is slightly heavier or lighter than the others. You have a classical balance with two pans. You are allowed to weigh only three ..... Click for details . Discussion . Solution
Q.3 How would you divide a SQUARE into three equal RECTANGLES with only three straight lines, without lifting your pen and without overlapping any line on any of the sides of the square? Click for details
Q.4 How would you store a three page long text on a metre stick? Click for more . Solution