Most interesting puzzles asked in interview. #1

Some common puzzles asked in technical interviews:

• Make 120 with 5 Zeros using mathematical operations?
• Make 120 with 4 Zeros using mathematical operations?
• In front of you is a balance. Your task is to devise a system, using 4 weights, so that any whole number of kilograms can be weighed up to 40 kg
• In front of you is a balance. Your task is to devise a system, using 4 weights, so that any whole number of kilograms can be weighed up to 80 kg
• Three ants are sitting at the three corners of an equilateral triangle. Each ant starts randomly picks a direction and starts to move along the edge of the triangle. What is the probability that none of the ants collide?
• There is a building of 100 floors-If an egg drops from the Nth floor or above it will break.-If it’s dropped from any floor below, it will not break. You’re given 2 eggs.Find N. How many drops you need to make? What strategy should you adopt to minimize the number egg drops it takes to find the solution?
• Mr X has 25 horses, and he want to pick the fastest 3 horses out of those 25. He has only 5 tracks that means only 5 horses can run at a time, even he don’t have a stop watch . What is the minimum number of races required to find the 3 fastest horses?