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This problem trains for: SAT-I, GMAT, AMC-8, Math Kangaroo 5-6, Math Kangaroo 7-8.
Lawrence Durrell was born when his mother was 26 years old. His youngest brother Gerald was born when their mother was 39 years old. When they were living in Corfu, their ages added up to 94. How old was Gerald at the time?
(characters from Gerald Durrell's "My Family and Other Animals")
The differences between their ages stay the same throughout their lives.
Denote Gerry's age at the time by g. Mother's age is:
Larry is 13 years older than Gerry:
Therefore, if we add the three ages together we get:
We know the sum of their ages to be:
and we can solve for Gerry's age:
Gerry's age was 14 at the time of the wonderful adventures he later described in his books.