Answer
$150$ unknown errors
Work Step by Step
To estimate the number of unknown errors still in the system, we can use a method called error seeding. Error seeding involves intentionally injecting a known number of errors into a system to estimate the total number of errors present.
Given that $S=100$ errors were intentionally placed in the system before final testing, and $r=50$ of these were discovered and corrected during final testing, it means that only $50$ of the intentionally placed errors remained undiscovered.
During final testing, a total of $D=200$ errors were discovered and corrected, including the 50 intentionally placed errors. The remaining $50$ seeded error are also fixed, so a total of $200+50=250$ errors. .
We can estimate that a similar proportion of unknown errors exists in the system:
$\frac{r}{S}=\frac{D}{x}$
$x=\frac{S\cdot D}{r}=\frac{100\cdot 200}{50}=400$.
Total estimated initially $= 400$. You have fixed $250$ known errors, so estimated remaining unknown errors:
$400-250=150$
