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Solved Example #6

Saturday, February 9th, 2013

Question : The sum of the reciprocals of the positive divisors of 120 ?

a.2

b.3

c.4

d.6

Answer : 

Sum of its factors = (1 + 2 + 4 + 8)(1 + 3)(1 + 5) = 360

Sum of the reciprocals of its factors = 360 / 120 = 3