Hmmm.....
I notice, though, if I get rationals via mathn, I do get what I want
(w/o patching):

irb(main):002:0> Math.sqrt(Rational(16,9))
=> 1.3333333333333333
irb(main):003:0> require 'mathn'
=> true
irb(main):004:0> Math.sqrt(Rational(16,9))
=> (4/3)
irb(main):005:0> Math.sqrt(16/9)
=> (4/3)

-- 
Posted via http://www.ruby-forum.com/.