Answer:
r = (11√π)/π
Explanation:
V = πr²h 
We are given V = 1089, and h = 9. Plug them into the formula and simplify
1089 = πr²(9)
 121 = πr² (divide by 9 on both sides)
 121/π = r² (divide by π on both sides)
 √(121/π) = r (take the square root of both sides)
 Now simplify √(121/π)
 (√121)/(√π)
 11/√π
 [11(√π)]/[(√π)(√π)]
 (11√π)/π
so r = (11√π)/π