Questions d'entretien

Entretien pour Intern

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Jane Street

Fit questions: Why do you want to be a trader? Why should/shouldn't we hire you? Math: 1. Flip a fair coin 8 times. What's the probability that the number of heads is a multiple of 3? 2. You mentioned on your resume that your favorite author is David Foster Wallace. Estimate the number of copies of Infinite Jest that have been read cover to cover. 3. You have a 2x1x1 brick. Define the distance between two points on the brick to be the infimum of the lengths of all paths between them on the brick. What is the maximum possible distance between two points on the brick?

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Réponses aux questions d'entretien

17 réponse(s)

13

The shortest path has length sqrt(6). sqrt(1^2 + 1^2) = sqrt(1 + 1) = sqrt(2) sqrt(2^2 + sqrt(2)^2) = sqrt(4 + 2) = sqrt(6)

Utilisateur anonyme le

5

If the farthest points are opposite corners, then wouldn't the shortest path be sqrt(10)? I'm not sure how you get 2*sqrt(2)

Utilisateur anonyme le

3

0 is a multiple of 3.

Paste le

2

The first answer, sqrt(2^2 + (1+1)^2) seems right I think.

Utilisateur anonyme le

4

Why not choose the centers of the opposing 1x1 sides for the farthest points? 3 > sqrt(8), right? And don't you have to include 8c0 for problem 1? So 85/256

Utilisateur anonyme le

1

Responding to GD on Mar 15, 2016: there could also be 0 heads since 0 is a multiple of 3. So the final answer should be 85/256

YH le

1

opposite corners: path1 using long sides sqrt(2^2+2^2)=sqrt(8) path2 using short side then long one sqrt(3^2+1^2)=sqrt(10) inf of two sqrt(8) path from center of short side to center of another short side = 0.5+2+0.5 = 3 From center to center, you cannot do shorter. 3 > sqrt(8) 3 is the max.

Ilya le

0

Can someone explain the answer further for me?

Utilisateur anonyme le

0

The poster who answered 3 is correct. The questions asks for paths on the surface of the brick, not through the center.

Utilisateur anonyme le

12

Farthest points are opposite corners. Shortest path has length sqrt(2^2+(1+1)^2)=2*sqrt(2)

Will le

1

i'm getting sqrt(6) I can't see how people are saying sqrt(8)

Utilisateur anonyme le

0

last one should be sqrt(10), since it is asking for paths on top of the brick, not going through the brick. In order to do this you must draw a layout of the brick, and connect the two furthest points, then you get a side of 2+1 and 1, using the pythagorean theorem you get sqrt(10.

Utilisateur anonyme le

0

oh i see now

Utilisateur anonyme le

1

2sqrt(2)

summer le

0

Isn't May 13 right in this case? Assuming distance is calculated as on the surface of the triangle

anonymous le

1

Last one is sqrt(10)

Utilisateur anonyme le

2

My boy, Pythagoras, would beg to differ about that sqrt(10) answer. Use his theorem twice to get sqrt(6)

Utilisateur anonyme le

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