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Value of a coin

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Value of a coin

by Aman verma » Mon Mar 01, 2010 3:13 am
Q:The value of a coin varies directly to the square of its radius,when its thickness is constant.What will be the radius of a coin if its value is $ 5.

I. The radius of a coin is 1.5 cm and its value is $ 2.

II.The coin is made of copper and the diameter of the coin is twice the radius of the coin.
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by Pedros » Mon Mar 01, 2010 3:39 am
Aman verma wrote:Q:The value of a coin varies directly to the square of its radius,when its thickness is constant.What will be the radius of a coin if its value is $ 5.

I. The radius of a coin is 1.5 cm and its value is $ 2.

II.The coin is made of copper and the diameter of the coin is twice the radius of the coin.
St 2 doesnt tell te value - radius relationship so insufficient.

St 1 : ( 1.5)^2 of radius gives the value of 2

so we calculate the radius of a coin with a value of 5 :

square root of :[( 1.5)^2 * 5 ]/ 2

is it A ?
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by GMATSUCKER » Mon Mar 01, 2010 11:43 am
I go for Atoo. Statement II. gives us nothing.
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by Aman verma » Tue Mar 02, 2010 10:56 am
Sol:A sitter indeed. Let V=value ,r=radius, K=proportionality constant.
Now V is proportional to r^2 i.e V=k.r^2
From statement I . we get 2 =k X 1.5^2 =>k=2/2.25 or k=8/9
Again 5=8/9 X r^2 or r = 2.4 cm (required radius). AnsA
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