Question

Susan is attending a talk at her son's school. There are 8 rows of 10chairs where 54 parents are sitting. Susan notices that every parent is either sitting on their own or next to just one other person. What is the largest possible number of adjacent empty chairs in a single row at that talk?

Answer 1

The largest possible number of adjacent empty chairs in a single row is 3

Explanation:

The parameters given are;

The number of chairs = 8 × 10 = 80 chairs

The number of parents = 54

Sitting arrangements of parents = Alone or to one other person

Therefore;

The maximum number of parents on a row = 1 + 1 + 0 + 1 + 1 + 0 + 1 + 1 + 0 + 1 = 7

Hence when the rows have the maximum number of parents occupying the seats we have for the 8 rows;

7 + 7 + 7 + 7 + 7 + 7 + 7 + 7 = 56

But there are only 54 parents, therefore, up to the 7th row will have 7 parents while the 8th row will have only 5 parents to make the possible sitting arrangement to be as follows;

7 + 7 + 7 + 7 + 7 + 7 + 7 + 5 = 54

The sitting arrangement for the 8th row is therefore

1 + 1 + 0 + 1 + 1 + 0 + 1 + 0 + 0 + 0

Hence there will be three empty seats in the 8th row making the largest possible number of adjacent empty chairs in a single row = 3.