CREATE TABLE table_39049 ("Unit" TEXT, "Russian" TEXT, "Translation" TEXT, "Ratio" TEXT, "Cubic inches  ( exact ) " TEXT, "Metric value" TEXT, "Imperial" TEXT, "US Customary" TEXT)

How big in metric terms is the unit that has a ratio of 1/20?
SELECT "Metric value" FROM table_39049 WHERE "Ratio" = '1/20'
SELECT "Metric value" FROM "table_39049" WHERE "Ratio" = '1/20'