### Related Rates Test Question: Circular Plate Heated

### Raw Transcript

Hello everyone Tom from EveryStepCalculus.com.

A related rates problem, number

8 in my book, calculus book. let’s do it.

index(8) to get to my menu. Average rate of

change is the same as related rates in my thinking.

I’m not a professor. And we want to do

in this problem number 8 is something to do with the circle.

So we’re gonna go, and the area, we’re gonna do Circle area here.

And here’s the,

related rates you always deal with a formula. And differentiate both sides with respect to T. So

here’s the formula for the area of a circle pie r squared.

And they give you radius in this problem they could give you diameter. I changed

that, I

try to catch everything that these professors try to trick you with.

And everything in physics and calculus is a trick,

memorization and tricks.

Enter radius given, okay we have to press alpha before we enter anything in

this

entry line here and my programs. And they give us at five centimeters.

I’ll take you through it and we’re asked to find the

change in area, that’s dA/dt with respect to time.

And we’re going to enter the rate,

rate they gave you, they always give you the rate of something.

And so we press alpha, and put in here .2

and its increasing.

And it’s per hours so we’re gonna choose number three.

So here we have dr/dt which is the radius which is

changing at .2 centimeters per hour. And the radius is five centimeters.

You change it if you want I always give you that option.

In case you made a mistake. And here’s what we’re doing with differentiating

left side area with the right side. And we come up with this 2 pie r dr/dt.

We add the variables right here which I show you.

calculation is 6.28 centimeters squared per hour.

Pretty neat huh? EveryStepCalculus.com Go to my site buy my programs

and pass calculus class.

And you’ll have these programs for the rest of your life your kids or grandkids or

yourself or neighbor or whoever. If you don’t then you

just memorize and forget like all college kids do.

Um so anyways go to my site

buy my program and pass calculus test but then maybe even

subscribe to me so you can catch other videos I make

or a blog here and there.

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