Radius Doubled

crystalbivens · #1 Jul 20, 2008, 09:59 AM

If the radius of a circle is doubled, by what factor will the area change?

Thanks

Unknown008 · Jul 20, 2008, 10:08 AM

According to the principle of proprotionality, it's by 4.

How? Well, you may insert into a certain radius, for example 2. Area will be pi (r^2), ie 4pi (we'll keep to pi to facilitate matters.).

Now, double the radius, ie 4. New area is pi(4^2) , ie 16pi.

You'll find out that the change in factor is squared the increase in radius (when you multiply that radius only though.)

Hope that helped!

crystalbivens · Jul 20, 2008, 10:13 AM

WOW this is all another language to me. Thanks for your help

Unknown008 · Jul 20, 2008, 10:17 AM

Hum, you know what is pi? $\pi$

crystalbivens · Jul 20, 2008, 10:32 AM

Not really i'm trying to learn on my own by reading and so far not so good.

Unknown008 · Jul 20, 2008, 06:22 PM

Well, this is an irrational number used in nearly all circular calculations including perimeter, area, volume of sphere, etc. You may come across it as $\frac{22}{7}$ or $3.14$ .



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