Sheep Pens
A Farmer has twelve sheep and decides to put each of them into a separate pen; but to make the pens he has only 12 long hurdles and 6 half length hurdles. How can he do it?
Answer  

The farmer needs to arrange the 12 long hurdles in the shape of a hexagon made of 6 triangles, and then use the six short hurdles to divide each triangle into two. Alan Butler spotted a solution which left a spare hurdle  can anyone improve on this? Tim Bray spotted a solution which had 4 spare hurdles, although I suspect he might have cut the hurdles!!!! Following my comments suggesting he may have cut some of the hurdles, Tim has come up with a couple of other solutions, which certainly don't need a saw. This one uses 11 long and 6 short, leaving one spare long hurdle This one uses 12 long and 4 short, leaving two spare hurdles. 
