Total number of hours in one day = 24
Number of hours people slept = 8
Part of the day people slept =
=
It is one-third part of a day.
Number of days in one ordinary year = 365
Number of hours in one day = 24
Number of hours in 365 days = 365 × 24
= 8760
Number of hours that people slept in 1 day = 8
Number of hours that people slept in 365 days = 365 × 8
= 2920
The part of the year that people slept =
=
So, people slept one-third of the year.
A man sleeps one-third part of an year.
Number of years a man of 60 years slept = 60 ÷ 3
= 20
Thus, a man of 60 years must have slept 20 years.