Five Dimensions

Geometry Level 3

The distance (in m e t e r s meters ) from the center to any vertex of a five dimensional hypercube with a five dimensional volume of 32 m e t e r s 5 32\:{meters}^{5} is a \sqrt{a} .

Find a a .


The answer is 5.

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4 solutions

Jackson Abascal
Nov 11, 2014

Just as the side length of a square is a r e a \sqrt{area} and the side length of a cube is v o l u m e 3 \sqrt[3]{volume} , we can find the side length of our hypercube with 32 5 = 2 \sqrt[5]{32}=2 . Setting the center of our hypercube to the relative coordinate (0, 0, 0, 0, 0) then lets us set a vertex coordinate at (1, 1, 1, 1, 1), since 1 is half of the side length. We can finally use the generalized distance formula to find the distance between these two points 1 2 + 1 2 + 1 2 + 1 2 + 1 2 = 5 \sqrt{{1}^{2}+{1}^{2}+{1}^{2}+{1}^{2}+{1}^{2}}=\boxed{\sqrt{5}}

Somesh Singh
Nov 24, 2014

a much easier solution to this problem is implied by repeating patterns in the value of the diagonal. For a 2d cube, i.e, a square, the diagonal is sqrt(2) times the side, for a 3d cube its sqrt(3) times the side, for a 4d cube (tesseract) its sqrt(4) or twice the edge (you can figure it out with just a little insight!!!). so for a 5d cube, which we obviously can't picture, the diagonal has to be sqrt(5) times the edge which in this problem would be 2. but the given distance is only half the diagonal, so d=2xsqrt(5)/2=sqrt(5) =>this value is given to be sqrt(a) so the value of a=5

as we can easily find out the length of each side is 2. (Using Pythagoras Theorem to find each diagonal) Consider a square, l=2, diagonal length= sqrt(2) vertex to centre, distance =sqrt(2)/2.

Cube, l=2, diagonal length sqrt(6) V to C = sqrt(6)/2

4th dimension, diagonal= sqrt(10) V to C = sqrt(10)/2

5th dimension diagonal = sqrt(14) V to C = sqrt(14)/2

Ravi Raj Gupta - 6 years, 6 months ago
Alex Gatchalian
Dec 1, 2014

d=2xsqrt(5)/2=sqrt(5) =>this value is given to be sqrt(a) so the value of a=5

Anna Anant
Nov 26, 2014

Let L = lenght of edge of the hypercube C = distance of vertices to the center (origin) Volume of hypercube is L^5 = 32, so L = 2 Distance of vertices from the center is C = sqrt (a) = L × sqrt (5) / 2 = sqrt (5); therefore a= 5

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