What is the probability that N points randomly chosen on the boundary of a circle lie in the same semicircle?
via Microsoft research

## Monthly Archives for May, 2013

## Label the wires

You have a cable of 1000 wires between two telephone exchanges A and B that are 10km apart. Unfortunately, the wires are not labeled, so you don't know how the endpoint of a wire at A corresponds to an endpoint at B. All you have is a battery and a light-bulb. Of course, you have tape and pen for labeling the wires.
What's the minimum distance …

**Continue reading the story**"Label the wires"## sum of digits

For a natural number k, let S(k) denote the sum of the digits of k in it's decimal representation. For example, if k=231, S(k)=2+3+1=6. Show that among 2 consecutive natural numbers n and n+1, atleast one of them can be written in the form k+S(k).
via Utah Math Puzzles

## Card betting puzzle

You play the following game: The game host has a shuffled deck of 52 cards: 26 red and 26 black. He keeps revealing one card at a time until all 52 cards are revealed. At any time, you can interrupt the host and bet that the next card is red. You get one and only one chance to bet. You HAVE to bet at some …

**Continue reading the story**"Card betting puzzle"## Umbrella sharing

In a rainy season , one day 3 huge ladies walking under a normal sized umbrella.
The umbrella is not huge enough to accommodate all 3 ladies yet not a single lady got wet.
Why ?
via Brain Teasers