In the auditorium, there are 21 seats in the first row and 29 seats in the second row. ths number of seats in a row continues to increase by 8 with each additional row.

813 seats

Step-by-step explanation:

Given that,

In the auditorium, the number of seats in the 1st row = 21

In the auditorium, the number of seats in the 2nd row = 29

Therefore, the increasing number of seats in each of the row = 8.

According to the question,

The number of seats in a row continues to increase by 8 seats with each additional row. For example, 29, 37, 45 etc.

To find the number of seats in the 100th row, we have to use statistical formula.

As 21 is the total seats in the 1st row, and there is an increase of 8 seats, the formula should be = 21 + (n - 1) × 8

we have to deduct 1 so that we get 99th rows seat numbers as we have to add 21 with that to find the 100th number row.

As the question is to determine the number of seats in the 100th row, therefore, n = 100.

The number of seats in the 100th row = 21 + (100 - 1) × 8 = 21 + 99 × 8

= 21 + 792 = 813 seats.

Quartiles are basically 25% markers, i.e. the median is the 2nd quartile as it represents the 50% marker.

Therefore the 3rd quartile is 75% - with 100 students, that means 75 students send less than 102 messages, and therefore approximately 25 students in the sample send more than 102 messages.
If you draw a frequency graph, you can draw the quartile markers in as vertical lines to divide up the data.