Comments on: Runway Math http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/ Daily posts of Excel tips…and other stuff Thu, 09 Feb 2012 18:06:07 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Tushar Mehta http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48308 Tushar Mehta Sun, 25 Jul 2010 23:44:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48308 <p>Two comments.</p> <p>Because of symmetry, the numbers in the 1st column only need to go up to 18. Hence, the formula in the 2nd column becomes =I2+18 (my first column of data was I starting with row 2).</p> <p>Unlike most, I prefer functionally equivalent arithmetic operations over string operations. I don't know the comparative costs (and it definitely wouldn't matter for such a small sample), but one reversed digits test is =MOD($J2,10)*10+INT($J2/10)=$I2</p> Two comments.

Because of symmetry, the numbers in the 1st column only need to go up to 18. Hence, the formula in the 2nd column becomes =I2+18 (my first column of data was I starting with row 2).

Unlike most, I prefer functionally equivalent arithmetic operations over string operations. I don’t know the comparative costs (and it definitely wouldn’t matter for such a small sample), but one reversed digits test is =MOD($J2,10)*10+INT($J2/10)=$I2

]]> By: Dick Kusleika http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48281 Dick Kusleika Sun, 25 Jul 2010 00:05:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48281 <p>I like to lull you to sleep with sparse posts. Then, when your expectations are reasonably low, I come out with some crap. In reality, I go through streaks. Sometimes I have a ton to say and sometimes nothing. I wish I knew what triggers that.</p> I like to lull you to sleep with sparse posts. Then, when your expectations are reasonably low, I come out with some crap. In reality, I go through streaks. Sometimes I have a ton to say and sometimes nothing. I wish I knew what triggers that.

]]> By: Chris Greaves http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48265 Chris Greaves Sat, 24 Jul 2010 13:41:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48265 <p>@Roy "Are you either out of work or suffering from insomnia?"<br> Neither. He is keeping me amused/informed! (grin!)</p> @Roy “Are you either out of work or suffering from insomnia?”
Neither. He is keeping me amused/informed! (grin!)

]]> By: Fun Fast Multiplication Trick! | Download Fun Games http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48241 Fun Fast Multiplication Trick! | Download Fun Games Fri, 23 Jul 2010 15:30:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48241 <p>[...] Daily Dose of Excel » Blog Archive » Runway Math [...]</p> [...] Daily Dose of Excel » Blog Archive » Runway Math [...]

]]> By: Roy MacLean http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48235 Roy MacLean Fri, 23 Jul 2010 10:29:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48235 <p>Dick, this is your seventh post in two weeks (and some are pretty substantial) - I haven't been able to keep up with reading them! Are you either out of work or suffering from insomnia? :-)</p> <p>/Roy</p> Dick, this is your seventh post in two weeks (and some are pretty substantial) – I haven’t been able to keep up with reading them! Are you either out of work or suffering from insomnia? :-)

/Roy

]]> By: Rick Rothstein (MVP - Excel) http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48231 Rick Rothstein (MVP - Excel) Fri, 23 Jul 2010 05:42:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48231 <p>I see I had a typo in my posted mathematical solution to this problem. Towards the end of my message, I had these three lines...</p> <p> 11L < 38</p> <p> Divide both sides by 9 yields this...</p> <p> L < 3.4545....</p> <p>If you were wondering why I said to divide both sides by 9, then you have company because I have no idea why I said that either. The obvious division is by 11, not 9... the indicated originally posted resulting inequality was correct though... 38 divided by 11 is indeed 3.4545...</p> I see I had a typo in my posted mathematical solution to this problem. Towards the end of my message, I had these three lines…

11L < 38

Divide both sides by 9 yields this…

L < 3.4545….

If you were wondering why I said to divide both sides by 9, then you have company because I have no idea why I said that either. The obvious division is by 11, not 9… the indicated originally posted resulting inequality was correct though… 38 divided by 11 is indeed 3.4545…

]]> By: Pete http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48222 Pete Thu, 22 Jul 2010 23:43:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48222 <p>@ Dick</p> <div style="overflow: auto; white-space: nowrap;" class="codecolorer-container text default"><div style="white-space: nowrap;" class="text codecolorer">=A1=RIGHT(B1)&LEFT(B1)</div></div> @ Dick

=A1=RIGHT(B1)&LEFT(B1)
]]> By: fzz http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48210 fzz Thu, 22 Jul 2010 20:51:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48210 <p>While it's possible to solve this algebraically, it's odd that anyone familiar with accounting would be unfamiliar with the fact that two numbers with adjacent transposed digits differ from each other by multiples of 9, e.g., 1234 and 1324 differ by 90, 1729 and 7129 differ by 5400.</p> <p>2-digit permutations which differ by 18 are those with separate digits differring by 2: 0-2, 1-3, 2-4, 3-5, 4-6, 5-7, 6-8, 7-9. Only 0-2 and 1-3 produce both 2-digit numbers in [1,36].</p> While it’s possible to solve this algebraically, it’s odd that anyone familiar with accounting would be unfamiliar with the fact that two numbers with adjacent transposed digits differ from each other by multiples of 9, e.g., 1234 and 1324 differ by 90, 1729 and 7129 differ by 5400.

2-digit permutations which differ by 18 are those with separate digits differring by 2: 0-2, 1-3, 2-4, 3-5, 4-6, 5-7, 6-8, 7-9. Only 0-2 and 1-3 produce both 2-digit numbers in [1,36].

]]> By: Charlie Rowe http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48207 Charlie Rowe Thu, 22 Jul 2010 20:19:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48207 <p>Sounds like a great puzzler for CarTalk.</p> Sounds like a great puzzler for CarTalk.

]]> By: Eric http://www.dailydoseofexcel.com/archives/2010/07/22/runway-math/#comment-48202 Eric Thu, 22 Jul 2010 18:31:00 +0000 http://www.dailydoseofexcel.com/?p=4062#comment-48202 <p>So I ran solver (needed to add a constraint that 10a+b and 10b+a were <=36) and came up with 2,0 as the possible results. Excluded a and b from being 0 and came up with 1,3. No other results.</p> So I ran solver (needed to add a constraint that 10a+b and 10b+a were <=36) and came up with 2,0 as the possible results. Excluded a and b from being 0 and came up with 1,3. No other results.

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