CREATE TABLE table_47721 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Ground" TEXT, "Crowd" FLOAT, "Date" TEXT)

Which Crowd has a Away team of sydney?
SELECT MAX("Crowd") FROM table_47721 WHERE "Away team" = 'sydney'
SELECT MAX("Crowd") FROM "table_47721" WHERE "Away team" = 'sydney'