SOLUTION: Find the average rate of change of the function A(X)=piX^2, where A is the area of a circle with radius X as the radius changes from X=4 to X=7. The correct answer is one of the

Algebra ->  Circles -> SOLUTION: Find the average rate of change of the function A(X)=piX^2, where A is the area of a circle with radius X as the radius changes from X=4 to X=7. The correct answer is one of the      Log On


   

Question 1198829: Find the average rate of change of the function A(X)=piX^2, where A is the area of a circle with radius X as the radius changes from X=4 to X=7.
The correct answer is one of the following. Which one is it?
A) 4pi
B) 7pi
C) 11pi
D) 16pi
Found 2 solutions by ikleyn, MathLover1:
Answer by ikleyn(52798) About Me  (Show Source):
You can put this solution on YOUR website!
.

Calculate A(4);  then calculate A(7),


then get the average change as  %28A%287%29-A%284%29%29%2F%287-4%29.

Happy calculations (!)

Everything in this assignment can be done mentally.



Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
A%28x%29=pi%2Ax%5E2

Average=%28A%28b%29-A%28a%29%29%2F%28b-a%29
where
a=4
b=7

find A%28a%29 and A%28b%29
A%284%29=pi%2A4%5E2
A%284%29=16pi
A%287%29=pi%2A7%5E2
A%287%29=49pi
then
Average=%2849pi-16pi%29%2F%287-4%29
Average=%2833pi%29%2F3
Average=11pi