C:\Projects>irb -v
  irb 0.9.6(09/06/30)

  C:\Projects>irb
  irb(main):001:0> 1.15*100
  => 114.99999999999999

I don't believe it's a standards issue so much as it is just a facet of floating point math in binary. Since you can't actually store 1.15, you can just store your series of fractions which sum up to something very close to 1.15, I don't have much knowledge of floating point but I'd assume it stops at some value within epsilon of 1.15. When you multiply that value by 100 that sub epsilon value is now large enough to no longer allow the language to automatically round it for display.

  irb(main):020:0> 1.15*100 > 115-Float::EPSILON
  => false
  irb(main):021:0> 1.15*100 > 115-(Float::EPSILON*100)
  => true

I'm assuming older IRB just had a wider acceptance range than epsilon perhaps.