Date post: | 31-Dec-2015 |
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Reverse the digit in the answer and add it to the original answer.
Keep the answer to yourself and don’t let others get to know it.
The number is 123. Reverse it becomes 321. Then 321 – 123 = 198 Now, reverse 198 to become 891. Then 891 + 198 = 1089.
In general, the 3-digit number is 100a + 10b + c.
Reverse it to become 100c + 10b + a. Subtract one number from the other
(100a + 10b + c) – (100c +10b + a)= 100a – a + 10b – 10b + c – 100c= 99a – 99c= 99 (a – c)
Since we need to keep the 99 (a – c) to be 3-digit, a – c ≥ 2.
Possible values are 2, 3, … ,9 Possible values for 99 (a – c) are 198,
297, 396, 495, 594, 693, 792, 891.
Check yourself if you have one of those numbers before the addition of its reverse…
Addition of those numbers and its reverse will always be equal to 1089.