Consider the sum: ABC + DEF + GHI = JJJ .If different letters represent different digits, and there are no leading zeros, what does J represent?

• The value of J must be 9.Since there are no leading zeros, J must be 7, 8, or 9. (JJJ = ABC + DEF + GHI= 14? + 25? + 36? = 7??)Now, the remainder left after dividing any number by 9 is the same as the remainder left after dividing the sum of the digits of that number by 9. Also, note that 0 + 1 + ... + 9 has a remainder of 0 after dividing by 9 and JJJ has a
  remainder of 0, 3, or 6. The number 9 is the only number from 7, 8 and 9 that leaves a remainder of 0, 3, or 6 if you remove it from the sum 0 + 1 + ... + 9. Hence, it follows that J must be 9.
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