The GCF of numbers is the greatest common factors between the numbers
The GCF of the years is 1
The intervals are given as: 13 years and 17 years
Factor both intervals (i.e. 13 and 17)
13 = 1 * 13
17 = 1 * 17
The common factor between both products is 1
So, we have:
GCF = 1
Hence, the GCF of the years is 1
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