We are trying to find the check digit shown by the red question mark in the barcode on the right.
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To make it easier to see let us change the digits in the even places to a green colour (diagram on right).
You add the digits in the even places: 7 + 0 + 6 + 0 + 0 + 3 = 16 and multiply the answer by 3. 16 X 3 = 48
(You always multiply by 3)
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Next we add the digits in the odd places (shown on the right in red) 9 + 9 + 2 + 0 + 0 + 4 + x We don't know what number goes where the question mark is so let's call it x for the moment.
So when we add these numbers we get 24 + x )
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Now we add these two answers (as shown below)
Green digits: 7+0+6+0+0+3 = 16 X 3 = 48
Red digits: 9+9+2+0+0+4+X = 24 + x
48+24+x = 72 + x
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If the sum in step 4 is a multiple of 10, the check digit is "0" (zero). Otherwise, subtract the sum in step 4 from the next highest multiple of 10.
80 is the next number after 72 which we can divide by 10.
So 80 - 72 = 8
So x must equal 8 |
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