Comments on: Maths powers failing me...
http://ask.metafilter.com/36897/Maths-powers-failing-me/
Comments on Ask MetaFilter post Maths powers failing me...Mon, 24 Apr 2006 07:34:50 -0800Mon, 24 Apr 2006 07:34:50 -0800en-ushttp://blogs.law.harvard.edu/tech/rss60Question: Maths powers failing me...
http://ask.metafilter.com/36897/Maths-powers-failing-me
Maths question: How can you make 25 using only the numbers 2,4,6,8? <br /><br /> A friend of mine has been stumped by this - and as a mathmatical illiterate so am I. Apparently you can use each number once and there is no requirement to use all of them. I am assuming there is some sort of cunning trick at the heart of this...post:ask.metafilter.com,2006:site.36897Mon, 24 Apr 2006 07:31:29 -0800prentizmathsquestionflumuxingBy: bhance
http://ask.metafilter.com/36897/Maths-powers-failing-me#571872
(8 x 3) + (2/2) ?comment:ask.metafilter.com,2006:site.36897-571872Mon, 24 Apr 2006 07:34:50 -0800bhanceBy: bhance
http://ask.metafilter.com/36897/Maths-powers-failing-me#571874
although I suppose the 2/2 violates the 'use once' clause ... (slinks back to coffee-less morning. $@#%)comment:ask.metafilter.com,2006:site.36897-571874Mon, 24 Apr 2006 07:36:07 -0800bhanceBy: pooya
http://ask.metafilter.com/36897/Maths-powers-failing-me#571876
ummm....where'd the 3 come from?comment:ask.metafilter.com,2006:site.36897-571876Mon, 24 Apr 2006 07:38:12 -0800pooyaBy: cardboard
http://ask.metafilter.com/36897/Maths-powers-failing-me#571877
4*6 + log(8+2 )= 24+1 = 25<br>
though technically that's ln(8+2)/ln(10) and you're using extra numbers...comment:ask.metafilter.com,2006:site.36897-571877Mon, 24 Apr 2006 07:40:57 -0800cardboardBy: poppo
http://ask.metafilter.com/36897/Maths-powers-failing-me#571880
(2/8) * (4+6) = 2.5<br>
<br>
almost?comment:ask.metafilter.com,2006:site.36897-571880Mon, 24 Apr 2006 07:41:44 -0800poppoBy: bhance
http://ask.metafilter.com/36897/Maths-powers-failing-me#571882
Ha. 3. Wow. Jesus.<br>
<br>
I'm seriously going for coffee before I walk off a cliff.comment:ask.metafilter.com,2006:site.36897-571882Mon, 24 Apr 2006 07:43:25 -0800bhanceBy: malp
http://ask.metafilter.com/36897/Maths-powers-failing-me#571883
((4 + 6)/8)^2 = 25/16<br>
<br>
Does that count?comment:ask.metafilter.com,2006:site.36897-571883Mon, 24 Apr 2006 07:43:55 -0800malpBy: miagaille
http://ask.metafilter.com/36897/Maths-powers-failing-me#571884
I think we need to know what kinds of operations are allowed. Only addition, subtraction, multiplication and division? Or other stuff, like logs above? How about roots and exponentials? Does sqrt count as a use of 2?comment:ask.metafilter.com,2006:site.36897-571884Mon, 24 Apr 2006 07:44:33 -0800miagailleBy: gleuschk
http://ask.metafilter.com/36897/Maths-powers-failing-me#571890
sqrt(8-(6/2))^4comment:ask.metafilter.com,2006:site.36897-571890Mon, 24 Apr 2006 07:53:04 -0800gleuschkBy: pooya
http://ask.metafilter.com/36897/Maths-powers-failing-me#571891
4! + (8-6)/2 = 25comment:ask.metafilter.com,2006:site.36897-571891Mon, 24 Apr 2006 07:53:56 -0800pooyaBy: miagaille
http://ask.metafilter.com/36897/Maths-powers-failing-me#571894
Usually in these types of questions only the four basic operations are allowed, but if we can use fancy stuff here's a suggestion:<br>
<br>
4! = 24<br>
8-6 = 2<br>
2/2 = 1<br>
24+1 = 25comment:ask.metafilter.com,2006:site.36897-571894Mon, 24 Apr 2006 07:54:29 -0800miagailleBy: public
http://ask.metafilter.com/36897/Maths-powers-failing-me#571900
<a href="http://www.danieltebbutt.com/countdown.html">There is no solution using only normal (+-/*) operators.</a>comment:ask.metafilter.com,2006:site.36897-571900Mon, 24 Apr 2006 07:59:28 -0800publicBy: poppo
http://ask.metafilter.com/36897/Maths-powers-failing-me#571904
ok i've thought of a good trick (if, say you're doing this on a piece of paper or a napkin):<br>
<br>
((4*8) - 6) * 2 = 52<br>
<br>
Now turn the piece of paper upside downcomment:ask.metafilter.com,2006:site.36897-571904Mon, 24 Apr 2006 08:04:59 -0800poppoBy: cribcage
http://ask.metafilter.com/36897/Maths-powers-failing-me#571912
Are you sure it's not a transcription error? If 6 becomes 5, then:<br>
<br>
5 + 2 = 7<br>
8 * 4 = 32<br>
32 - 7 = 25comment:ask.metafilter.com,2006:site.36897-571912Mon, 24 Apr 2006 08:14:24 -0800cribcageBy: handee
http://ask.metafilter.com/36897/Maths-powers-failing-me#571921
4! + sin(8) = 24.989358247 (radians)<br>
or<br>
4! + cos(2) = 24.999390827 (degrees)<br>
<br>
or even better<br>
4! + cos(8-2-6) = 25comment:ask.metafilter.com,2006:site.36897-571921Mon, 24 Apr 2006 08:28:01 -0800handeeBy: mdn
http://ask.metafilter.com/36897/Maths-powers-failing-me#571946
<i>ummm....where'd the 3 come from?</i><br>
<br>
6/2?comment:ask.metafilter.com,2006:site.36897-571946Mon, 24 Apr 2006 08:42:43 -0800mdnBy: mdn
http://ask.metafilter.com/36897/Maths-powers-failing-me#571949
ie, 8 x (6/2) + (4/4)comment:ask.metafilter.com,2006:site.36897-571949Mon, 24 Apr 2006 08:43:22 -0800mdnBy: ancientgower
http://ask.metafilter.com/36897/Maths-powers-failing-me#571999
square root of (6/2)^2 + (8-4)^2, i.e., the Pythagorean theoremcomment:ask.metafilter.com,2006:site.36897-571999Mon, 24 Apr 2006 09:14:40 -0800ancientgowerBy: handee
http://ask.metafilter.com/36897/Maths-powers-failing-me#572045
er, ancientgower - doesn't that make 5?comment:ask.metafilter.com,2006:site.36897-572045Mon, 24 Apr 2006 09:50:22 -0800handeeBy: treeshade
http://ask.metafilter.com/36897/Maths-powers-failing-me#572046
how about w/ just 2,4,6?<br>
6 upside down and reversed is a 9<br>
9 + 4^2 = 25comment:ask.metafilter.com,2006:site.36897-572046Mon, 24 Apr 2006 09:50:44 -0800treeshadeBy: edd
http://ask.metafilter.com/36897/Maths-powers-failing-me#572049
handee can drop his last cos for an extra factorial, should one wish to avoid trig. Otherwise, I'd have suggest something like poppo's method.comment:ask.metafilter.com,2006:site.36897-572049Mon, 24 Apr 2006 09:52:16 -0800eddBy: Steven C. Den Beste
http://ask.metafilter.com/36897/Maths-powers-failing-me#572055
(6+(2/8))*4 == 25comment:ask.metafilter.com,2006:site.36897-572055Mon, 24 Apr 2006 09:53:48 -0800Steven C. Den BesteBy: TimeFactor
http://ask.metafilter.com/36897/Maths-powers-failing-me#572061
S C D B!comment:ask.metafilter.com,2006:site.36897-572061Mon, 24 Apr 2006 10:00:31 -0800TimeFactorBy: loquax
http://ask.metafilter.com/36897/Maths-powers-failing-me#572105
<em>(6+(2/8))*4 == 25<br>
</em><br>
A solution fiendishly clever in its intricacies.comment:ask.metafilter.com,2006:site.36897-572105Mon, 24 Apr 2006 10:28:54 -0800loquaxBy: poppo
http://ask.metafilter.com/36897/Maths-powers-failing-me#572127
crap! i spent ten minutes staring at .25, just <em>knowing</em> that that was related to the solution. curse you, steven c. den beste!comment:ask.metafilter.com,2006:site.36897-572127Mon, 24 Apr 2006 10:42:49 -0800poppoBy: Oddly
http://ask.metafilter.com/36897/Maths-powers-failing-me#572150
Poppo just made the 25th comment, and no math was involved. My brain, she a'splode!comment:ask.metafilter.com,2006:site.36897-572150Mon, 24 Apr 2006 10:59:54 -0800OddlyBy: inkyz
http://ask.metafilter.com/36897/Maths-powers-failing-me#572230
Here's another one: ((2+8)/.4)comment:ask.metafilter.com,2006:site.36897-572230Mon, 24 Apr 2006 12:16:13 -0800inkyzBy: dness2
http://ask.metafilter.com/36897/Maths-powers-failing-me#572231
related to SCDB, (6+4)*(2/8)comment:ask.metafilter.com,2006:site.36897-572231Mon, 24 Apr 2006 12:19:58 -0800dness2By: poppo
http://ask.metafilter.com/36897/Maths-powers-failing-me#572243
<em>Here's another one: ((2+8)/.4)<br>
posted by inkyz at 12:16 PM PST on April 24 [!]</em><br>
<br>
No<br>
<br>
<em>related to SCDB, (6+4)*(2/8)<br>
posted by dness2 at 12:19 PM PST on April 24 [!] </em><br>
<br>
Nocomment:ask.metafilter.com,2006:site.36897-572243Mon, 24 Apr 2006 12:27:36 -0800poppoBy: hades
http://ask.metafilter.com/36897/Maths-powers-failing-me#572566
A few years ago I wrote a quick perl script to brute-force the answer to a very similar puzzle. It's <a href="http://www.elsewhere.org/tmp/2468_pl.txt">here</a>, if anyone's interested.comment:ask.metafilter.com,2006:site.36897-572566Mon, 24 Apr 2006 18:33:27 -0800hadesBy: rob511
http://ask.metafilter.com/36897/Maths-powers-failing-me#572619
poppo, <a href="http://ask.metafilter.com/mefi/36897#572230">inkyz</a>'s solution <i>is</i> correct (as are <a href="http://ask.metafilter.com/mefi/36897#571891">pooya</a>'s and, as noted above, <a href="http://ask.metafilter.com/mefi/36897#572055">SCBD</a>'s).comment:ask.metafilter.com,2006:site.36897-572619Mon, 24 Apr 2006 19:27:46 -0800rob511By: muddgirl
http://ask.metafilter.com/36897/Maths-powers-failing-me#572648
I don't think inkyz's solution technically counts, since he diviced 4 by 10 before he used it. SCDB's solution is "the best one" because it only uses multiplication, division, addition, and subtraction.comment:ask.metafilter.com,2006:site.36897-572648Mon, 24 Apr 2006 20:22:28 -0800muddgirlBy: nomis
http://ask.metafilter.com/36897/Maths-powers-failing-me#572655
The problem with <a href="http://ask.metafilter.com/mefi/36897#572230">inkyz</a>'s solution is that 6 is not used.comment:ask.metafilter.com,2006:site.36897-572655Mon, 24 Apr 2006 20:35:22 -0800nomisBy: rob511
http://ask.metafilter.com/36897/Maths-powers-failing-me#572760
nomis, according to prentiz's question, "there is no requirement to use all of the [four numbers]." And muddgirl, if using a decimal point doesn't count (even though the challenge didn't mention notation), then pooya's use of 4! (or 4 <small><small>•</small></small> 3 <small><small>•</small></small> 2 <small><small>•</small></small> 1) fails too, even though both their solutions were quite creative.<br>
<br>
prentiz?comment:ask.metafilter.com,2006:site.36897-572760Tue, 25 Apr 2006 00:09:45 -0800rob511By: poppo
http://ask.metafilter.com/36897/Maths-powers-failing-me#572841
<em>poppo, inkyz's solution is correct</em><br>
<br>
um, inkyz uses ".4". this is NOT the same as "4"<br>
<br>
even if it was, what is the answer to inkyz solution? -15 ?<br>
<br>
<br>
<em>(as are pooya's and, as noted above, SCBD's).</em><br>
<br>
pooya's, yes if we are allowing all kinds of operands<br>
<br>
we still haven't heard from prentiz, but for my money, Steven is the only one who got it.comment:ask.metafilter.com,2006:site.36897-572841Tue, 25 Apr 2006 06:17:08 -0800poppoBy: handee
http://ask.metafilter.com/36897/Maths-powers-failing-me#573878
And mine. <br>
4! + cos(8-2-6) = 25<br>
Nobody said anything about "no trig".comment:ask.metafilter.com,2006:site.36897-573878Wed, 26 Apr 2006 03:49:17 -0800handeeBy: handee
http://ask.metafilter.com/36897/Maths-powers-failing-me#573879
Although obviously Steven wins.comment:ask.metafilter.com,2006:site.36897-573879Wed, 26 Apr 2006 03:49:42 -0800handeeBy: Steven C. Den Beste
http://ask.metafilter.com/36897/Maths-powers-failing-me#574307
Yay! So where's my check mark?comment:ask.metafilter.com,2006:site.36897-574307Wed, 26 Apr 2006 11:38:18 -0800Steven C. Den Beste