Issue #19321 has been updated by nobu (Nobuyoshi Nakada). The newer result seems arithmetically correct. ---------------------------------------- Bug #19321: BigDecimal multiplication giving different result since Ruby 3.1 https://bugs.ruby-lang.org/issues/19321#change-101107 * Author: alexandruanca (Alexandru Anca) * Status: Open * Priority: Normal * ruby -v: 3.1.3 * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- I have this math operation 120.to_d * 0.07 and I noticed that since upgrading to Ruby 3.1 I get different results. I would expect to get the same result as in previous versions. ``` rbenv local 3.0.3 ➜ irb require 'bigdecimal/util.rb' (120.to_d * 0.07).to_s('F') => "8.4000000000000012" ``` ``` rbenv local 3.1.3 ✗ irb require 'bigdecimal/util.rb' (120.to_d * 0.07).to_s('F') => "8.4" ``` It looks like the change has been introduced in Ruby 3.1. I tested Ruby 2.7.0 and I get the same result as in 3.0 ("8.4000000000000012") I saw in the release notes that there were changes to bigdecimal so I am not sure if this is expected or it's a bug -- https://bugs.ruby-lang.org/