Question

Decrypt the word “xqjjud” mathematically with a shift of 5

Answer 1

To make all of this more mathematical, consider the following conversion table for the English alphabet:

$$\def\arraystretch{1.5} \begin{array}{c} 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 \\ A & B & C & D & E & F & G & H & I \\ \\ 9 & 10 & 11 & 12 & 13 & 14 & 15 & 16 & 17 \\ J & K & L & M & N & O & P & Q & R \\ \\ 18 & 19 & 20 & 21 & 22 & 23 & 24 & 25 \\ S & T & U & V & W & X & Y & Z \\ \end{array}$$

i. Using the table, we can represent the letters in our message “xqjjud” with their corresponding numbers: $23 \ \ 16 \ \ 9\ \ 9\ \ 20\ \ 3.$

ii. Now subtract 5 (the encryption key) to each number to get: $18 \ \ 11 \ \ 4\ \ 4\ \ 15\ \ 24.$

iii. Now use the table to replace these numbers with their corresponding letters: "sleepy"