Suppose a U.S. Postal Service money order is numbered x4839203210, where the first digit is obscured. What is the missing digit?

Name: Suppose a U.S. Postal Service money order is numbered x4839203210, where the first digit is obscured. What is the missing digit?
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Question

Quizplus · Accepted Answer

The sum of the digits in the money order number must be divisible by 10. The sum of the visible digits is 4 + 8 + 3 + 9 + 2 + 0 + 3 + 2 + 1 = 32. The missing digit must be 4, so that the sum of the digits is 36, which is divisible by 10.