## Problem 39 of Monte Carlo solutions to Fifty Challenging Problems...

(This is another part of the Fifty Problems series, a set of example applications of Monte Carlo methods. In each post, I present source code which answers a probabilistic question using simulated models of the underlying system.)

Problem 39: a set of glass rods, with one end blue-dotted and the other red-dotted, are dropped. Many break into 3 parts. What is the average length of the blue-dotted pieces of these broken-in-three rods?
```#!/usr/bin/env ruby TRIALS=100000 # Much like 42 and 43, this is pretty trivial cum_blue = 0.0 TRIALS.times { # Choose two breaking points b1 = rand() b2 = rand() # put them on a stick reasonably... if (b1 > b2) x = b1 b1 = b2 b2 = x end # and let's say the blue is always on the left # that is, the length of the blue segment is b1 cum_blue += b1 } puts "After #{TRIALS} trials, average length:" puts cum_blue/TRIALS ```

I've been coding my way through Fifty Challenging Problems in Statistics with Solutions. This post is a part of the Fifty Challenging Problems series.

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