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Edit summary for version 13 :

Version 12

Version 13

Idiom #65 Format decimal number

From real value x in [0,1], create its percentage string representation s with one digit after decimal point. E.g. 0.15625 -> "15.6%"

Idiom #65 Format decimal number

From real value x in [0,1], create its percentage string representation s with one digit after decimal point. E.g. 0.15625 -> "15.6%"

Code
s = "%.1f%" % 100.0 * x
Doc URL
http://ruby-doc.org/core-2.2.3/String.html#method-i-25