There are 50 red marbles in one jar and 50 blue marbles in another jar. You need to rearrange them in such a manner that the probability of picking a red marble will be the highest. How will you do that?

A shopkeeper sells a pen for 12Rs. The customer gives him a 20Rs note. The shopkeeper does not have change. So he goes to a nearby shp, gets the change and gives 8Rs back to the customer. After sometime the other shopkeeper comes and tells him that the 20Rs note is fake. How much does the shopkeeper loose?

Two trains enter a tunnel 200 miles long (yeah, its a big tunnel) travelling at 100 mph at the same time from opposite directions. As soon as they enter the tunnel a supersonic bee flying at 1000 mph starts from one train and heads toward the other one. As soon as it reaches the other one it turns around and heads back toward the first, going back and forth between the trains until the trains collide in a fiery explosion in the middle of the tunnel (the bee survives). How far did the bee travel?

You have 100 doors in a row that are all initially closed. You make 100 passes by the doors starting with the first door every time. The first time through you visit every door and toggle the door (if the door is closed, you open it, if its open, you close it). The second time you only visit every 2nd door (door #2, #4, #6). The third time, every 3rd door (door #3, #6, #9), etc, until you only visit the 100th door. What state are the doors in after the last pass? Which are open which are closed?