Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_21958 ( "Name" text, "Map colour" text, "First operated" real, "Type" text, "Length" text, "No. Sta" real, "Current Stock" text, "Future Stock" text, "Trips per annum (\u00d71000)" real, "Avg. trips per mile (\u00d71000)" real )

### Question ###
When turquoise is the map colour how many avg. trips per mile ( 1000) are there?

### Accurate SQL ###

SELECT COUNT("Avg. trips per mile (\u00d71000)") FROM table_21958 WHERE "Map colour" = 'Turquoise'