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Multiples of 6 (Posted on 2024-02-22) Difficulty: 2 of 5
The number 24 is a multiple of 6, and its reversal, 42, is also a multiple of 6.

What is the probability that the reversal of any randomly-chosen multiple of 6 is also a multiple of 6?

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Solution Benford's Law | Comment 3 of 9 |
I am feeling a bit contrary today, so I will give a different answer.

I agree that the reverse of an integer divisible by 6 is also divisible by 6 if the initial digit was 2 or 4 or 6 or 8.

And I agree that the initial digit is even approximately 4 times out of 9 (44.4%) if you are considering all 3 digit or 4 digit or 5
 digit numbers.

But what if you consider all integers less than 200,000?  Then only 22.2% start with an even digit.

And what if you consider all numbers between a random x and y, or all numbers without an upper bound?  Benford's law arguably says that 17.6% of numbers start with a 2, 9.7% with a 4, 6.7% with a 6 and 5.1% with an 8.  so, adding them up, my answer is 39.1%.

  Posted by Steve Herman on 2024-02-22 11:25:07
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