CREATE TABLE table_name_42 (number_on_map INT, name VARCHAR, construction_commenced VARCHAR)

What is the average number for Northgate which commenced its construction before 1951?
SELECT AVG(number_on_map) FROM table_name_42 WHERE name = "northgate" AND construction_commenced < 1951
SELECT AVG("number_on_map") FROM "table_name_42" WHERE "construction_commenced" < 1951 AND "name" = "northgate"