closest_minutes.rb

# returns the closest 15 minute interval
def closest(n)
  closest_interval = [0, 15, 30, 45, 60].map { |m|
    [m, (m - n).abs]
  }.min_by { |_, minutes_away|
    minutes_away
  }
  closest_interval.first
end

%w(1 7 14 16 27 30 33 44 55).each { |x|
  p closest(x.to_i)
}