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Re M2417
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16 Sep 2014, 00:21



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Re: M2417
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16 Dec 2014, 22:50
Bunuel wrote: Official Solution:
A diameter of a figure is defined as a maximum distance AB where points A, B belong to the figure. For example, the diameter of the parallelogram is the parallelogram's longer diagonal. If the diameter of the cube is 3, what is the area of the surface of the cube?
A. 3 B. 6 C. \(6\sqrt{3}\) D. 18 E. \(12\sqrt{3}\)
If \(x\) is the length of the edge of the cube, the diameter of the cube is \(\sqrt{x^2 + x^2 + x^2} = 3\). From this equation, \(x = \sqrt{3}\). The area of the surface \(= 6(\sqrt{3})^2 = 18\).
Answer: D Hi, i am unable to understand this step. diameter of the cube is \sqrt{x^2 + x^2 + x^2} = 3would you please elaborate. Thank you



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Re: M2417
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16 Dec 2014, 23:41
arunpkumar wrote: Bunuel wrote: Official Solution:
A diameter of a figure is defined as a maximum distance AB where points A, B belong to the figure. For example, the diameter of the parallelogram is the parallelogram's longer diagonal. If the diameter of the cube is 3, what is the area of the surface of the cube?
A. 3 B. 6 C. \(6\sqrt{3}\) D. 18 E. \(12\sqrt{3}\)
If \(x\) is the length of the edge of the cube, the diameter of the cube is \(\sqrt{x^2 + x^2 + x^2} = 3\). From this equation, \(x = \sqrt{3}\). The area of the surface \(= 6(\sqrt{3})^2 = 18\).
Answer: D Hi, i am unable to understand this step. diameter of the cube is \sqrt{x^2 + x^2 + x^2} = 3would you please elaborate. Thank you The longest length in a cube of \(\sqrt{sum of square of 3 sides}\), which will be equal to the length of longer diagonal of parallelogram ie 3 refer to the figure.. Attachment: Untitled.jpg To find the length of the BlackLine, you need to know the length Red line and yellow line Length of red line: \(\sqrt{x^2+x^2}=\sqrt{2x}=b\) length of Yellow line =x So length of Black line =\(\sqrt{(b)^2+x^2}=\sqrt{3x}= 3\) This can be Refer to the chapter of 3D geometries to get a better idea math3dgeometries102044.html#p792331
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Re: M2417
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06 Sep 2016, 04:19
Your question states "If the diameter of the cube is 3, what is the area of the surface of the cube?" Answer should be A
Area of surface = \sqrt{3^2} Total surface area = 6 \sqrt{3^2}



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06 Sep 2016, 04:24



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30 Apr 2018, 02:24
+1 for option D. The diagonal of a cube is a*(sqrt3). a=sqrt(3). Surface area of the cube is 6*a*a. The surface area is 6*3 or 18. Hence option D it is ...
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Re: M2417
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19 Aug 2018, 21:53
Bunuel wrote: Official Solution:
A diameter of a figure is defined as a maximum distance AB where points A, B belong to the figure. For example, the diameter of the parallelogram is the parallelogram's longer diagonal. If the diameter of the cube is 3, what is the area of the surface of the cube?
A. 3 B. 6 C. \(6\sqrt{3}\) D. 18 E. \(12\sqrt{3}\)
If \(x\) is the length of the edge of the cube, the diameter of the cube is \(\sqrt{x^2 + x^2 + x^2} = 3\). From this equation, \(x = \sqrt{3}\). The area of the surface \(= 6(\sqrt{3})^2 = 18\).
Answer: D Hi Bunuel, request you to explain why \(\sqrt{x^2 + x^2 + x^2} = 3\) ... I do not follow this...
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19 Aug 2018, 22:47
ENEM wrote: Bunuel wrote: Official Solution:
A diameter of a figure is defined as a maximum distance AB where points A, B belong to the figure. For example, the diameter of the parallelogram is the parallelogram's longer diagonal. If the diameter of the cube is 3, what is the area of the surface of the cube?
A. 3 B. 6 C. \(6\sqrt{3}\) D. 18 E. \(12\sqrt{3}\)
If \(x\) is the length of the edge of the cube, the diameter of the cube is \(\sqrt{x^2 + x^2 + x^2} = 3\). From this equation, \(x = \sqrt{3}\). The area of the surface \(= 6(\sqrt{3})^2 = 18\).
Answer: D Hi Bunuel, request you to explain why \(\sqrt{x^2 + x^2 + x^2} = 3\) ... I do not follow this... Check below: a^2 + a^2 = d^2 (where d is the length of the diagonal of the base) d^2 + a^2 = D^2 (where D is the longer diagoanal). Substitute d^2 to get (a^2 + a^2) + a^2 = D^2 > \(\sqrt{a^2 + a^2 + a^2} = D\). Attachment: mainqimge4e631d93f476069c499529cdc215a32.png
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Re: M2417
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09 Nov 2018, 08:11
Bunuel please help, I can't find my mistake... My understanding: diameter of cube = 3D diagonal of cube 3D diagonal of cube = a * \(\sqrt{3}\) "diameter of the cube is 3" (prompt) > 3 = a * \(\sqrt{3}\) > a = \(\frac{3}{\sqrt{3}}\) and not \(\sqrt{3}\) area of surface: 6 * \(a^2\) = 6 * \((\frac{3}{\sqrt{3}})^2\) = 18 so I get the same end result but a different value for the side of cube a










