Answer:
i belive it is A (2x)2/3
Step-by-step explanation:
I think your question should read "A circle has an AREA of 81 PI square units...)
Circle Area = PI * radius^2
81 PI = PI * radius ^2
radius^2 = 81 PI / PI
radius^2 = 81
radius = 9
Therefore circle diameter = 9 * 2 = 18
*FORMULA*
Qu1.

Height=10
Base=8


Qu2.
Area of a kite=half×product of digonals
Step by step solution
Summation of 1st diagonal =5+5
=10
Summation of 2nd diagonal =7+5
=12
Product of the diagonals
=10×12
=120
Area=1÷2×120
=60