get_grade inject

gistfile1.rb

def get_grade(array)
  average = array.inject(:+).to_f / array.length

  case average
  when 0..59
    "F"
  when 60..69
    "D"
  when 70..79
    "C"
  when 80..89
    "B"
  when 90..100
    "A"
  end
end