Here she's 11 years old: Here it's a 16 year old Judy Garland playing an 11 year old Dorothy Gale. This is largely unnoticed unless the viewer has read the book.
Here she's 10 years old: The year is 1895. Dorothy Gale is ten years old, living in a one-room cabin she shares with her Uncle Henry and Aunt Em, a dusty, threadbare existence in the flat and windswept fields of Kansas. A violent storm carries her off to the undiscovered country of Oz, an island full of short, rugged people who live under the watchful eyes of sorcerers.