CREATE TABLE table_27713890_1 (no_in_series NUMBER, us_viewers__millions_ VARCHAR2)

Wha episode number in the series had 24.8 million u.s. viewers?
SELECT MIN(no_in_series) FROM table_27713890_1 WHERE us_viewers__millions_ = "24.8"
SELECT MIN("no_in_series") FROM "table_27713890_1" WHERE "24.8" = "us_viewers__millions_"