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If the word “BRIGHT” is coded as” OCPLKV”, then how will you code the word “SERIAL”?

1) CDKYFG
3) CKDGFY
2) FPYNDN
4)FPNDYN

5) none of these Can someone give me the answer with a little explanation?

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    "That only works..." Absolutely true, and without any further information about the method of encryption, the problem has no answer: SERIAL could be encoded into _any_ sequence of six letters (including the four listed, and so "None of the above" is also not a correct answer to the question).2012-09-13

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If you map the letters of the words "BRIGHT" and "OCPLKV" to numbers using the obvious encoding A = 1, B = 2, ..., Z = 26, you get $2, 18, 9, 7, 8, 20$ and $15, 3, 16, 12, 11, 22.$ If you now subtract the former sequence from the latter, what's left is $13, -15, 7, 5, 3, 2.$ Assuming that the cipher is using arithmetic modulo 26, the −15 becomes 26 − 15 = 11, leaving us with the sequence $13, 11, 7, 5, 3, 2.$ Does that look familiar? What do you get when you add these numbers modulo 26 to the letters of the word "SERIAL", encoded into numbers as above? (Hint: it's one of the four choices.)