In the following sum, the digits 0 to 9 have all been used.

O = Odd, E = Even (zero is even).

The top row's digits add to 9.

Can you determine each digit?

Puzzle Copyright © Kevin Stone

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Hint

The first digit in each row is even, so the first column can only be 2 + 8, 4 + 6, 4 + 8, 6 + 8 (either way around, and it must be a total over 9).

Answer

423 + 675 = 1098.

Reasoning

Remembering that:

even + even = even

odd + odd = even

even + odd = odd

To discuss individual letters, it's easiest to represent the sum as:

A B C

D E F +

————————

G H I J

A and D are both even, and can only be 2 + 8, 4 + 6, 4 + 8, 6 + 8 (either way around, and it must be a total over 9), so the carry can only be 1, so G = 1.

Since column 2 is even + odd = odd, there can be no carry from column 1 (since even + odd + 1 is always even). Therefore, neither C nor F (both odd) can be 7 or 9 (otherwise there would be a carry), so C and F are 3 and 5 (but we don't yet know which is which), therefore J = 8.

Because A + D is even there can't be a carry from column 2, therefore E can't be 9 as this would force a carry. Therefore, I = 9. So, B can't be 0. Therefore, H = 0.

The last remaining odd number makes E = 7. Making B = 2.

Therefore, A and D are 4 and 6 (but we don't yet know which is which).

Since the top row's digits have to add to 9 the top number must be 423.

This makes the sum 423 + 675 = 1098.