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PROJECT EULER · #0285

Pythagorean Odds

Statement only · SolvedOriginal problem ↗

Albert chooses a positive integer k, then two real numbers a,b are randomly chosen in the interval [0,1] with uniform distribution.
The square root of the sum (ka+1)2+(kb+1)2 is then computed and rounded to the nearest integer. If the result is equal to k, he scores k points; otherwise he scores nothing.

For example, if k=6, a=0.2 and b=0.85, then (ka+1)2+(kb+1)2=42.05.
The square root of 42.05 is 6.484 and when rounded to the nearest integer, it becomes 6.
This is equal to k, so he scores 6 points.

It can be shown that if he plays 10 turns with k=1,k=2,,k=10, the expected value of his total score, rounded to five decimal places, is 10.20914.

If he plays 105 turns with k=1,k=2,k=3,,k=105, what is the expected value of his total score, rounded to five decimal places?

Write-up coming later

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