Sometimes the data given for finding a mean is in a table. The table below shows the number of pets owned by 21 different people.

The total number of people = 7 + 6 + 5 + 2 + 1 = 21.

From the table 7 people have 0 pets = total 0 pets.
                       6 people have 1 pet = total 6 pets.
                       5 people have 2 pets = total 10 pets.
                       2 people have 3 pets = total 6 pets.
                       1 people have 4 pets = total 4 pets.

Total number of pets = 0 + 6 + 10 + 6 + 4 = 26 pets on total.