Have you heard of Kumbhakarna, the brother of Ravana? He is famous for sleeping for half a year.
Most people sleep about 8 hours a day.
Then what part of a day is it? _________

So what part of a year do they sleep? A person 60 years old must have slept ________ years!!!

Total number of hours in one day = 24
Number of hours people slept       =   8
Part of the day people slept           = $\frac{8}{24}$
                                                       = $\frac{1}{3}$
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 = $\frac{2920}{8760}$

                                                             = $\frac{1}{3}$
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.