Problem: “John is interested in the history of his family. He sees from family recordsthat his great-grandmother was born on 25 October 1879, and she died on 13 December 1945. How old was she when she died?”

Write and discuss why the problem can be written as 1879 + ? = 1945.

Model 1879 and 1945 on an open number line and insert 1900 on the number line. Discuss the solution. “From 1879 to 1900 is 21, and from 1900 to 1945 is 45. So great  grandmother was 21 + 45 = 66 years old when she died.” Record this on the board or  modelling book.

Problem: “Jonah Rogers was born on 12/03/1823 and died on 14/09/1891. How old  was he when he died?”

Discuss why 1891 – 1823 is a suitable calculation to make, which reduces to finding 91 – 23. Record the answer on the board or modelling book.

Examples: “How long did these people live?” Record the answers on the board or modelling book.

Born                Died
21/09/1853      17/11/1901

13/11/1937      01/12/1980

01/03/1899      12/12/1987

28/04/1848      01/05/1924

30/08/1888      1/09/1923

23/05/1902      21/07/1933

Problem: “On a tour of England, Malcolm Smith finds the gravestone of one of hisancestors, which reads “Joseph Smith. Born 22nd July 1638. Died 12th April 1665.”

How old was Joseph when he died?”

Discuss why 1665 – 1638 = 27 produces an answer that is one too large (because 12th  April precedes 22nd July). So Joseph was 26 when he died. Challenging examples:

“How long did these people live?” Record the answers on the board or modelling book.

Born                Died
21/12/1943    12/01/2003
13/12/1956    01/12/1991
01/03/1856    12/12/1911
28/09/1924    12/01/2002
30/08/1878    21/03/1922
23/12/1919    21/07/1991