By far the most popular and well-stocked category of used instruments is our selection of guitars, where we've got a huge variety of all the big names. Used Gibson Les Paul, pre-owned Fender Telecaster and secondhand Stratocaster guitars are commonly found within these pages, waiting for their new homes with players and collectors.
22/7 is a pretty decent choice for teaching 11-year-olds about fractions that are close to pi. 355/113 would be better, if you think they can remember numbers that big. And approxRational is fun. Exercise for the interested reader: implement an inverse to approxRational.
We can make our first estimate of Pi from the known ratios From the given triangle; we know that the ratio of the diameter (AB) to one side of the hexagon (CB) is 1/2 so our initial (low) estimate of the value of Pi is 6/2 or 3.00.