If 20% of all manually filed returns contain errors, and 0.05% of all electronically filed returns contain errors, how much more likely is a manual filer to make an error than an electronic filer?

Convert the percentages to decimals: 20% = 0.20 and 0.05% = 0.0005. Divide 0.20 by 0.0005 to get 400, so a manual filer is 400 times more likely to make an error; the correct choice is “400 times more likely.”

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