Answer:
The oldest age of Olivia’s sister can be 11 years.
Step-by-step explanation:
Given: Olivia’s sister’s age is x years.
To write: inequality that can be used to represent the given situation.
As Olivia is 6 years older than her sister,
Olivia's age 
As the sum of their ages is no more than 28 years,

So, the oldest age of Olivia’s sister can be 11 years.
N= pi
2nr=C
C=94.2
94.2/2=nr
47.1=nr
47.1/n=r
15=r
2r = D
2(15)=30
Your answer is 30 inches