quant skills ( VAR, greek analysis?)

Are the questions like "What's 92 times 34?" to measure how many registers you have in your brain or something? I think I do OK with those.

Now, the logic and probability questions.. I can't say I nailed any of them though I've worked through them with interviewer help. I'm not sure if that counts for anything.

Are there any good resources for working through a bunch of puzzle problems like these? (I mean hundreds, not just a few problems)
 
Quote from WallstYouth:

With 3 weights, you can identify the heaviest ball. For n balls, you can identify the heaviest ball after x times where x is the largest integer such that 2^x <= n
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That was some nice brologic there...
3 weights does not guarantee you get the odd-ball: you need n attempts to guarantee you get the light ball. Now you only ever need to compare 2 balls and the moment you have 2 that are different weights, the lighter one is the odd-ball obviously.

The fact remains the complexity of that runtime is O(n).



Regards,
 
Quote from krazykarl:

That was some nice brologic there...
3 weights does not guarantee you get the odd-ball: you need n attempts to guarantee you get the light ball. Now you only ever need to compare 2 balls and the moment you have 2 that are different weights, the lighter one is the odd-ball obviously.

The fact remains the complexity of that runtime is O(n).



Regards,
More...

Try re-thinking this one but consider that you can weigh more than 2 balls at a time.
 
Quote from krazykarl:

That was some nice brologic there...
3 weights does not guarantee you get the odd-ball: you need n attempts to guarantee you get the light ball. Now you only ever need to compare 2 balls and the moment you have 2 that are different weights, the lighter one is the odd-ball obviously.

The fact remains the complexity of that runtime is O(n).



Regards,
More...
Bollocks, who said you can only weigh one ball against another?

1). Weigh 7 against other 7. Pick heaviest group.

2). Remove one ball from heavy group, and weigh 3 against 3. If these are equal then the removed ball is the heaviest and you have found it in 2 weighings. If not, pick the heaviest group of 3 balls from the weighing.

3). Remove one ball from the selected heavier group of 3. From these 2, Weigh 1 against 1. If they are different you found the heaviest ball. if they are equal, then the heaviest is the one you removed.

There you go, guaranteed to find the heaviest ball in max of 3 weighings, (2 if you get lucky, but not guaranteed).

You're welcome.
 
Assuming the ball is catching up with the wall (it would have to be since it eventually hits it) and moving at 60 MPH relative to the wall which is moving 120 MPH, it will then bounce backward at 60 MPH relative to the wall, and subsequently be stationary in space.

Answer = Zero.
 
Quote from WallstYouth:

Here are typical question we use to filter out retards, I work for a prop desk at an IBank as a developer not really Quant but I've seen similar questions used for many quant roles:

Question: Given arbitrary integer, come up with a rule to judge if it is divisible by 9. Prove it.

Question: Roll a penny around another fixed penny in the center with edges in close contact. After moving half circle around the center penny, you will find the penny in motion has rotated 360 deg. Why?

Question: very heavy wall moving at 60mph, a ball moving same direction at 120 mph. What is direction and speed of ball after ball hit wall.

Question: A square with four corners A,B,C,D. Suppose you start from corner A and have equal chance to go to neighboring corners B and D; After reaching new corner, you again have equal chance to go to its two neighboring corners. The time consumed to travel on each edge is 1, what is the mean time to come back to A.

Question: What is the properties of where p is prime number larger than 3

Question: A stair of 100 steps. You can either climb either one step or two steps but no more each time and you can walk up entire stair any way you like with rule above obeyed. How many possible combinations of ways to finish the walk?

Question: Given variances and covariance of X and Y. Z=a*X+b*Y. Calc variance of Z.

Question: There are 14 identical-looking balls. 13 of them have the same weight while one of them is heavier than the rest. What is the minimum times you can weight to identify the heaviest ball ? How do you generalize for n balls
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What's the point? You can be a sucessful trader without knowing the answer to any of these. If you want to be a quant, well that's another story.
 
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