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# A store sells wrapping paper only in square sheets of integer length.

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Math Expert
Joined: 02 Sep 2009
Posts: 57083
A store sells wrapping paper only in square sheets of integer length.  [#permalink]

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17 Sep 2018, 22:17
00:00

Difficulty:

95% (hard)

Question Stats:

29% (02:46) correct 71% (02:27) wrong based on 25 sessions

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A store sells wrapping paper only in square sheets of integer length. If Robert has to wrap a cylinder of radius 3 centimeters and height 5 centimeters, what is the length, in centimeters, of the smallest sheet he can buy?

A. 13
B. 12
C. 10
D. 8
E. 7

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GMAT 1: 670 Q47 V34
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Re: A store sells wrapping paper only in square sheets of integer length.  [#permalink]

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18 Sep 2018, 14:19
2
careful not to assume on this question.
nowhere does it say you have to keep the square sheet hole when wrapping (though normal people do wrap with 1 piece)
so what they are basically asking is:
what's the surface area of this cylinder? what answer gives you AT LEAST this surface area

if we ballpark PI at 3 we have
for the side: 5*(2*PI*3)= 5*(2*3*3) = 90

for the top and bottom of the cylinder we have
PI*3^2 = 3*9 = 27

total surface area: 90 + 2*27 = 144

now this equals to 12^2
however keep in mind that we ballparked PI as being 3, while it's actually 3,14...
so the total surface area is actually more than 144

as such the answer has to be a sheet with a side of 13, which gives you a total surface area of 169

kudos if you like
Re: A store sells wrapping paper only in square sheets of integer length.   [#permalink] 18 Sep 2018, 14:19
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