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I recently came across a classic maths riddle: "A two-digit number plus its reverse equals 121. What could the number be?" This type of puzzle is a great way to engage students or anyone interested in numbers because it combines algebraic thinking with logical deduction. To solve it, you can start by letting the two-digit number be represented as 10x + y, where x is the tens digit and y is the units digit. Its reverse would then be 10y + x. According to the puzzle, their sum is 121: (10x + y) + (10y + x) = 121 Simplifying, you get: 11x + 11y = 121 Dividing both sides by 11: x + y = 11 This means the sum of the digits equals 11. Now, since x and y are digits (0-9), possible pairs for (x,y) are (2,9), (3,8), (4,7), (5,6), (6,5), (7,4), (8,3), and (9,2). Each pair forms a two-digit number such as 29, 38, 47, 56, 65, 74, 83, or 92. If you check any of these numbers added to their reverse, for example 65 + 56 = 121, they satisfy the condition. So, all these numbers where the digits sum to 11 are solutions. I found this puzzle particularly useful for teaching the importance of variables and the power of simple equations. It’s not only about getting the answer but understanding the process. Plus, discussing puzzles like this helps develop critical thinking and problem-solving skills in a fun and interactive way.”