Add new comment
Want facts and want them fast? Our Maths in a minute series explores key mathematical concepts in just a few words.
What do chocolate and mayonnaise have in common? It's maths! Find out how in this podcast featuring engineer Valerie Pinfield.
Is it possible to write unique music with the limited quantity of notes and chords available? We ask musician Oli Freke!
How can maths help to understand the Southern Ocean, a vital component of the Earth's climate system?
Was the mathematical modelling projecting the course of the pandemic too pessimistic, or were the projections justified? Matt Keeling tells our colleagues from SBIDER about the COVID models that fed into public policy.
PhD student Daniel Kreuter tells us about his work on the BloodCounts! project, which uses maths to make optimal use of the billions of blood tests performed every year around the globe.
Let's omit the first stage of Kaprekar's algorithm and just look at what happens when the only rearrangement is reversing the digits in three of the numbers he looks at and doing a repeated operation.
Find the absolute difference between a number and its reverse, and then the difference between that and its reverse, and so on.
2005, 2997, 4995, 999
1789, 8082, 5274, 549, 396, 297, 495, 99
6174, 1458, 7083, 3276, 3447, 3996, 2997, 4995, 999
The absolute difference between the reverses of these repnines gives us our kernel, which is zero. That's true of all palindromes of course, though the operation in the algorithm producing a palindrome won't necessarily lead to a kernel. For example, consider summing them instead
1789, 11660, 18271, 35552, 61105, 111221, 233332
6174, 10890, 20691, 40293, 79497
Lastly standard number line subtraction:
2005 ... (17 steps!) ... -8939779398
1789, -8082, -10890, -20691, -40293, -79497
6174, 1458, -7083, -10890, -20691, -40293, -79497 (A negative number can be regarded as a palindrome, eg -121 = 0-121-0)
Look at 6174 still behaving mysteriously, what's more in cahoots with that other notorious number 1089.