How is the check digit of a DEA number calculated?

How is the check digit of a DEA number calculated?

• A. Sum of digits in positions 2,4,6; multiply by 2; add positions 1,3,5
• B. Sum of digits in positions 4,6,8, multiplied by 2, plus the sum of digits in positions 1,3,5
• C. Sum of all digits
• D. Multiply all digits and use the last digit

Answer: (B)

The check digit is made from a weighted sum of the numeric part of the DEA number to help verify the value and catch mistakes. Specifically, take the digits that follow the two letters and form the seven-digit block. The digits in positions 4, 6, and 8 of the full string (which correspond to the even positions within that seven-digit block) are doubled, then you add the digits in positions 1, 3, and 5 (the odd positions within the block). The total you get, look at its units digit—that is the check digit. In other words, for a seven-digit block a b c d e f g, you compute 2*(b + d + f) + (a + c + e), and the check digit is the last digit of that total. This method provides a simple way to detect common input errors. Other options don’t follow this weighting pattern or use operations that wouldn’t yield a reliable check digit, such as summing all digits or multiplying all digits.

The check digit is made from a weighted sum of the numeric part of the DEA number to help verify the value and catch mistakes. Specifically, take the digits that follow the two letters and form the seven-digit block. The digits in positions 4, 6, and 8 of the full string (which correspond to the even positions within that seven-digit block) are doubled, then you add the digits in positions 1, 3, and 5 (the odd positions within the block). The total you get, look at its units digit—that is the check digit.

In other words, for a seven-digit block a b c d e f g, you compute 2*(b + d + f) + (a + c + e), and the check digit is the last digit of that total. This method provides a simple way to detect common input errors.

Other options don’t follow this weighting pattern or use operations that wouldn’t yield a reliable check digit, such as summing all digits or multiplying all digits.