A few days ago
SherWall94

# Need help with this math problem?

A Two Hundred Dubloon Coin is unique in that the outer edge is gold while the inside is silver. Assuming both sides of the coin are identical, and a line tangent to the inner circle is 23 mm from edge to edge of the coin, and excluding the edge of the coin in the calculation, what is the surface area of gold on the coin, in square millimetres? Please round up to the nearest square millimetre.

Top 4 Answers
A few days ago
Twiggy

Favorite Answer

This question has been asked a number of times. Why don`t you look through the questions, and you will find the answer ?

You may find the better answers in the maths section.

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A few days ago
zanthus
I think you left something out in the question.

Actually, I would say ZERO millimeters. The question states that GOLD is only on the outer edge. Then, is asks to find the surface area of the gold, EXCLUDING the edge of the coin.

Since the gold is only on the edge, and we are excluding the edge, the answer is zero.

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A few days ago
krishbhavara
Let the radius of the inner circle be “r” and the outer circle be “R”

Surface area covered with gold

= Area of the inner circle – Area of the outer Circle

= ÏR^2 – Ïr^2

= Ï (R^2 – r^2)

The image

http://s122.photobucket.com/albums/o275/theedifier/?action=view¤t=doubloon-1.jpg

AB is the length of the tangent drawn touching the inner circle

= 33 mm

Draw OC perpendicular to AB

Thereby, OC bisects AB

==> AD = DB = 11.5 mm

In the right angled triangle ODB

OB = r (Radius of the inner circle)

OD = R (Radius of the outer circle)

DB = 11.5 mm

By pythagerous theorem

OB^2 = OD^2 + DB^2

==> r^2 = R^2 – (11.5)^2

==> (11.5)^2 = R^2 – r^2

Thus, the Surface area covered with gold

= Ï (R^2 – r^2)

= Ï (11.5)^2

If it is double sided required area = 2 * Ï (11.5)^2

http://www.theedifier.com/

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A few days ago
♥Abby♥
2! no, i’m jk, sorry chica, i cant help u w/ that!
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