Deleting multiple key and value pairs from hash in Rails

Question

number = {:a => 1, :b => 2, :c => 3, :d => 4}

upon evaluation of certain condition i want to delete key-value pair of a,b,c

Answer 1

number.delete "A"
number.delete "B"
number.delete "C"

Or, less performant but more terse:

number.reject! {|k, v| %w"A B C".include? k }

Answer 2

or, more performant than second Chris' solution but shorter than first:

%w"A B C".each{|v| number.delete(v)}