How many provinces joined Canada after 1900?

Question

How many provinces joined Canada after 1900?

Answer 1

Provinces:

1 September 1905  Saskatchewan and Alberta

31 March 1949  Newfoundland (later renamed Newfoundland and Labrador)

Territory:

1 April 1999  Nunavut

Answer 2

Three

1905 Saskatchewan

1905 Alberta

1949 Newfoundland  (They changed their name to Newfoundland and Labrador in 1964)

Although I have difficulty when you say joined Canada.  The literal answer going by the definition of "joined" is the colony of Newfoundland.  Saskatchewan and Alberta were divided out of Northwest Territories in 1905.  But NWT were part of Canada since 1870.  The answer you are looking for is still probably 3.