This constellation with a ranking of 51 has how many percentages on record?
CREATE TABLE table_21910 (
    "Rank" real,
    "Family" text,
    "Abbre\u00adviation" text,
    "Constellation" text,
    "Area (sq.deg.)" text,
    "Area (msr)" text,
    "Per\u00adcent\u00adage" text,
    "Right ascension (hm)" text,
    "Decli\u00adnation (dm)" text,
    "Quad" text
)
SELECT COUNT("Per\u00adcent\u00adage") FROM table_21910 WHERE "Rank" = '51'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: This constellation with a ranking of 51 has how many percentages on record? ### Input: CREATE TABLE table_21910 (
    "Rank" real,
    "Family" text,
    "Abbre\u00adviation" text,
    "Constellation" text,
    "Area (sq.deg.)" text,
    "Area (msr)" text,
    "Per\u00adcent\u00adage" text,
    "Right ascension (hm)" text,
    "Decli\u00adnation (dm)" text,
    "Quad" text
) ### Response: SELECT COUNT("Per\u00adcent\u00adage") FROM table_21910 WHERE "Rank" = '51'