Tax returns filed manually have a 20% chance of containing errors, while tax returns filed electronically have a 0.05% chance of containing the same. If 2.7 million tax returns are filed each way, how many more erroneous manually filed returns will there be than erroneous electronically filed returns?

Manually filed returns have an error rate of 20%, so 2,700,000 × 0.20 = 540,000 erroneous returns. Electronically filed returns have an error rate of 0.05% (0.0005), so 2,700,000 × 0.0005 = 1,350. The difference is 540,000 − 1,350 = 538,650, so the correct choice is 538,650.

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