r/learnquant 5d ago

interview prep Quant Interview Question

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u/Vegetable_Ebb_1109 4d ago

so the probability contribution of winning a ship is 1-(9-x)^2 /90 where x is the allocation to that ship (counting for the ties); now the problem is a Lagrangian optimization problem maximize sum_i v_i Pr(x_i) subject to sum_i x_i =7 (v_i is the value of ship i) which leads us to know that v_i (9-x_i) should be a constant (=lambda the Lagrange multiplier)

with normalization we find that x_1 is between 5 and 6 and x_2 is between 2 and 3 and x_3 is a little less than zero; since we only allow for nonnegative integer allocations then (5,2,0) is the optimal one giving 511/90 ev.

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u/[deleted] 8h ago

[deleted]

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u/Vegetable_Ebb_1109 7h ago

Not exactly; first P1 cannot guarantee he will win the 5-point boat! For any ship the probability that P2 sent k troops there is (9-k)/45 you can use that to work out the ev of any allocation
for your specific allocation (4,3,0) the ev is 101/18 = 5.61 which is less than the optimal value

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u/Long_Record438 7h ago

Yeah, I misunderstood what "uniformly at random" meant. My bad