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December 20, 2014

December 20, 2014

Posted by **CJ** on Thursday, January 27, 2011 at 7:17am.

The diameter of the Dome of the Rock in Jerusalem is 20m. If it is plated with gold that is 5cm thick, find the cost of plating the dome in gold given that 1kg of gold costs $43,395 and 1g of gold is equal to 19.3cm>3

p.s cm>3 means cm cube

- geometry -
**Damon**, Thursday, January 27, 2011 at 7:43amsurface area of sphere = (4/3) pi r^2

so

surface area of hemisphere = (2/3)pi r^2

here r = 10 m

so

surface area = (200/3) pi meters^2

there are 10^4 cm^2 per meter^2

so

surface area = (200/3) pi*10^4 cm^2

volume = surface area * depth

= (200/3) pi *10^4 * 5 cm^3

grams = volume*density

= (200/3) pi *10^4 * 5 (1/19.3)

cost per gram = 43.395

so

cost = (200/3) pi *10^4 * 5 (1/19.3)*43.395

- geometry -
**drwls**, Thursday, January 27, 2011 at 7:52amThe volume of the gold would be

V = (pi/4)D^2*(thickness) = 15.7 m^3

= 15.7*10^6 cm^3

The mass would be (density)*V = 303.2 *10^6 g = 303.2*10^3 kg

Multiply that by the cost per kg.

I get about 13 billion dollars

- geometry -
**drwls**, Thursday, January 27, 2011 at 7:59amI treated it as a 5 cm layer over a cylinder. Damon treated it as a hemisphere. He is correct.

http://www.historyofscience.com/G2I/timeline/images/dome_of_the_rock.jpg

- geometry -
**CJ**, Thursday, January 27, 2011 at 9:55amthank you sooo much damon :)

- GOLD DUST FOR SALE -
**BENSON IMO**, Tuesday, January 17, 2012 at 4:47amGOLD DUST FOR SALE

Dear Sir/ Madam,

We are small scale Gold miners here on the sub-region of West Africa. We have some huge

quantity of alluvial Gold Dust for sale at a considerable price of $30,500USD per kilo

which is below world market price, 22 carat and 92.05% purity. If you are interested, do

not hesitate to get back to us as soon as possible for us to give you our full co-operate

offer (FCO)

Best Regards

MR BENSON IMO

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