Posted by Denis Borris on October 24, 2002 at 16:54:49:
In Reply to: Re: brain teaser posted by Jack on October 24, 2002 at 11:30:35:
Since it's a "teaser":
divide a large pen into 3 pens: so you have 3 pens inside 1 pen;
using inside pens: put 1 cow in one, 3 cows in another, 17 cows in the last one;
the original big pen contains 21, right?!
you can make this more interesting with 19 cows, and prime number inside each
of the 4 pens: 3,5,11 so 19 in the big pen.