gets.chomp find a string in a list

Is it possible to find a string in a list for a gets.chomp for if, elsif?

def number_problem()

  puts "Please enter a number 1-100 for a phrase or word back!"
  number = gets.chomp

  mult_of_three = ["3", "6", "9", "12", "15", "18", "21", "24", "27", "30", "33", "36", "39", "42", "45", "48", "51", "54", "57", "60", "63", "66", "69", "72", "75", "78", "81", "84", "87", "90", "93", "96", "99"]
  mult_of_five = ["5", "10", "15", "20", "25", "30", "35", "40", "45", "50", "55", "60", "65", "70", "75", "80", "85", "90", "95", "100"]
  mult_of_both = ["15", "30", "45", "60", "75", "90"]

  if number == mult_of_three
    puts "Bit"