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<p>[QUOTE=&quot;-jeffB, post: 1639551, member: 27832&quot;]<i>Exactly</i> 1/10000, I&nbsp; believe.</p><p><br /></p><p>To get a &quot;radar&quot; number, the last four digits have to reverse the first four digits; the middle digit is always the same as itself, so it doesn&#039;t count. So, to simplify, pretend we&#039;ve got eight-digit numbers.</p><p><br /></p><p>Pick any four-digit number -- WXYZ. There will be 10,000 eight-digit numbers that start with WXYZ, from WXYZ0000 to WXYZ9999. Exactly one of those will be WXYZZYXW.</p><p><br /></p><p>Now, think about nine-digit numbers. There will be 100,000 nine-digit numbers that start with WXYZ, from WXYZ00000 to WXYZ99999. Exactly ten of those will be WXYZ0ZXYW, WXYZ1ZXYW, ..., WXYZ9ZXYW. So, again, one in 10,000.[/QUOTE]</p><p><br /></p>

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