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Let x = total number of errors.
Anne has a 300/x chance of spotting each error, Edward has a 100/x chance, and Isaac has a 200/x chance.
The total number of errors missed is equal to x times each of the editor's chances to miss an error.
x - 404 = x * (x-300)/x * (x-200)/x * (x-100)/x
x - 404 = (x^3 - 600x^2 + 110000x - 6000000)/x^2
0 = -196x^2 + 110000x - 6000000
0 = (x-500)(-196x + 12000)
x = 500
They missed 96 errors out of 500.
This is based on a problem I have seen before, except I added a third editor. |
