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please solve the problem no . 3 (at the top) with proper exp

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by Anurag@Gurome » Tue Feb 14, 2012 8:18 pm
ruplun wrote:please solve the problem no . 3 (at the top) in the attached pdf file with proper explanation...

Thanks in Advance
Radius of the cylinder = 6 implies that the radius of the base, which is a circle is also 6 units.
So, area of the base (which is a circle) = (pi) * Radius² = (pi) * 6² = 36(pi) sq units.
The label with width x has the same area as that of the base circle. Length of the label = 2 * (pi) * 6 = 12(pi) units.
Area of the label = Area of the base circle
So, 12(pi)x = 36(pi) or x = 3.

The correct answer is A.
Last edited by Anurag@Gurome on Tue Feb 14, 2012 9:07 pm, edited 1 time in total.
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by [email protected] » Tue Feb 14, 2012 9:02 pm
Shouldn't the length of the label be = 2pi*6 since it is wrapped around the cylinder once completely.
Then area of label = 12pi*x

Since this is equal to area of the base of cylinder we have 12pi*x = 36Pi
Hence x = 3.
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by Anurag@Gurome » Tue Feb 14, 2012 9:08 pm
[email protected] wrote:Shouldn't the length of the label be = 2pi*6 since it is wrapped around the cylinder once completely.
Then area of label = 12pi*x

Since this is equal to area of the base of cylinder we have 12pi*x = 36Pi
Hence x = 3.
That's right Amit, edited the reply. Thanks for pointing!
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by ruplun » Tue Feb 14, 2012 10:33 pm
how come the Length of the label = 2 * (pi) * 6 = 12(pi) units.
please explain..
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by Anurag@Gurome » Tue Feb 14, 2012 10:37 pm
ruplun wrote:how come the Length of the label = 2 * (pi) * 6 = 12(pi) units.
please explain..
The label is wrapped around the cylinder, whose base is circular. This means if we find the circumference of the circle, we know the length of the label.
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