Answer:
(a) Average growth​ factor = [tex](Geometric\ mean)^{\frac{1}{3}}[/tex]
                      = [tex](1.085\times1.041\times1.027)^{\frac{1}{3}}[/tex]
                      =  [tex](1.1599)^{\frac{1}{3}}[/tex]
                      = 1.05068
(b) Single percentage growth rate = (Average growth factor - 1) × 100
                             = (1.05068 - 1) × 100
                             = 5.068 %
(c) The mean of 8.5%, 4.1% and 2.7% = [tex]\frac{8.5 + 4.1 + 2.7}{3}[/tex]
                               = 5.1%
Therefore, the single percentage growth rate is not the same as the mean of 8.5%, 4.1%, and 2.7%.