Racket (aka PLT Scheme):

  $ racket
  Welcome to Racket v5.0.1.
  > (+ .1 .2)
  0.30000000000000004
  > (+ 1/10 2/10)
  3/10

Steel Bank Common Lisp:

  $ sbcl
  This is SBCL 1.0.43 [...elided]
  * (+ .1 .2)
  
  0.3
  * (+ 1/10 2/10)
  
  3/10