Question 1203952
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Estimate the instantaneous rate of change in the area of a circle 
when the radius is 3 cm. The formula for the area of a circle is A=πr^2
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The problem is posed incorrectly.


<pre>
The formula for the instantaneous rate of change the area of a circle is

    {{{(dA)/(dt)}}} = 2πr*r'(t),

where r(t) is the current radius of the circle as a function of t. 
</pre>

In order for the problem could be solved, the instantaneous rate r'(t) should be given
or should be calculated from other given data, but such data are missed in the problem.


The "solution" by the other person is INCORRECT and is an example of incorrect teaching.


For safety of your mind, simply ignore that "solution" as if you never seen it.