user: Question: How many cities had a census of 400000 in 1940?
Columns: ['Rank', 'City', '1890 census', '1910 census', '1920 census', '1930 census', '1940 census']
Types: ['real', 'text', 'text', 'real', 'real', 'real', 'real']
Sample row: [1.0, 'Keijō', '1,165,000', 230000.0, 247000.0, 350000.0, 1100000.0]
SQL:

assistant: SELECT COUNT("Rank") FROM "Table" WHERE "1940 census" = 400000.0;