How many items are listed for U.S. viewers for episode number 5 in the series?
CREATE TABLE "table1_27910411_1" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_millions" text
);
SELECT COUNT("u_s_viewers_millions") FROM "table1_27910411_1" WHERE "no_in_series"=5;