10.75 is the answer.
Step-by-step explanation:
First we will arrange the given data in ascending order.
8.2 , 9.1 Â , 10.75, 11.5
The values that divide each part of any given data set are called the first, second, and third quartiles and denoted by Q1, Q2, and Q3, respectively.
The third quartile is also called the upper quartile.
So, the upper quartile here is 10.75.