Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_76 (ratio INTEGER, similar_iso_a_size VARCHAR)
### Question:
Which Ratio has a Similar ISO A size of a3?
### Answer:
SELECT AVG(ratio) FROM table_name_76 WHERE similar_iso_a_size = "a3"