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**lakeheadca****Member**- Registered: 2010-01-31
- Posts: 37

how to find the diameter of the given figure.

thank you so much guys, specially bobby who always help so fast. He is great.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

specially bobby who always help so fast. He is great.

Yea, he is, when I grow up I want to be him.

We need to find r of the small circle. Fortunately there is a relationship that does all the work. There is an easier one that relates r to the heights but I am too lazy to look for it.

Where B1 is the area of the smaller circle. B2 is the area of the larger circle. h1 = height from the apex to smaller circle and h2 to the larger.

Do you see that it contains the little r we need. Like magic.

Cross multiply:

Divide both sides by pi.

Divide both sides by 144:

r = 6 and r = -6

Can't have a radius of - 6 so r = 6 and d = 2r = 12.

diameter of smaller circle is 12

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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**lakeheadca****Member**- Registered: 2010-01-31
- Posts: 37

Amazing !!!

(Thanks * 1000)

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

Hi lakeheadca;

Glad to help. Bring more!

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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