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vaivish
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 Posted: Tue Aug 05, 2008 10:51 am Post subject: ps 2 |
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. The side surface of a cylinder is reeled with a rectangular plate. If the height of a cylinder tank is 12 feet and the perimeter of the circular base is 9 feet, what is the diagonal of the rectangular plate?
(A) 13
(B) 15
(C) 18
(D) 20
(E) 21
Oa is B |
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malolakrupa
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| Posted: Tue Aug 05, 2008 6:36 pm Post subject: |
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Since the rectangular plate is reeled , the height becomes the length and the perimeter of the circular base becomes the breadth and using the famous theorem for right angle triangles ,
diagonal^2 = length^2 + base^2 we get diagonal = 15 which is B. |
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vaivish
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| Posted: Thu Aug 07, 2008 11:07 am Post subject: |
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| see 9 is perimeter so the diameter would be 9/pia. so how can we use 9^@ in the equation to get 15 as ans... |
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Stuart Kovinsky
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| Posted: Thu Aug 07, 2008 11:50 am Post subject: |
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| vaivish wrote: | | see 9 is perimeter so the diameter would be 9/pia. so how can we use 9^@ in the equation to get 15 as ans... |
The base of the rectangle IS the perimiter of the circle - there's no need to calcluate the circle's diameter.
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vaivish
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| Posted: Sat Aug 09, 2008 6:49 am Post subject: |
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| can you explain this one please. as i know perimeter is 2*pia* r. So how can it be the base of SQuare. if u draw the diagram it will be more clear to u. Thanks in advance |
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raunekk
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| Posted: Sat Aug 09, 2008 8:17 am Post subject: |
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u dont have to use 2 * pie * r...
the circumference of the base of clyinder= the width of the rectangle
height of the cylinder= length of the rectangle.
the diagonal wll be given by d pythagoras theorem. |
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andes1
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| Posted: Sat Aug 09, 2008 6:49 pm Post subject: |
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????
the circumference of the base of clyinder= the width of the rectangle ???
reeled???
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Stuart Kovinsky
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| Posted: Sat Aug 09, 2008 7:34 pm Post subject: |
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| andes1 wrote: | ????
the circumference of the base of clyinder= the width of the rectangle ???
reeled??? |
"Reeled" is a strange word that I wouldn't expect to see on the real GMAT, but it means "wrapped around".
In other words, you form the rectangle by cutting a straight line down the side of the cylinder and laying out the cylinder flat along the ground. (Picture a piece of paper wrapped all the way around a can - if you were to lay the paper flat, it would be a rectangle.)
So, the height of the cylinder becomes the height of the rectangle and the perimiter of the base of the cylinder ends up becoming the base of the rectangle.
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andes1
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| Posted: Mon Aug 11, 2008 3:16 pm Post subject: |
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thanks a lot
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