'A family consists of grandparents, parents and three grandchildren. The average age of

"A family
consists of grandparents, parents and three grandchildren. The average age of
the grandparents is 67 years, that of the parents is 35 years and that of the
grandchildren is 6 years. What is the average age of the family?
`28 4/7`
years (b) `31 5/7`
years (c) `32 1/7`
years (d) None of these"

average