Maths Puzzles

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oxo_foxo
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Maths Puzzles

Post by oxo_foxo » Wed Aug 12, 2009 6:25 pm

OK, this is probably a really inappropriate post to put in the 'boffins' section, because I really don't know very much about maths at all. I'm not much of a boffin. I do find it lovely though.
I am a trainee teacher (primary school) and in maths lessons, one of my favourite things to do is give the children maths puzzles, like problem solving puzzles.

For example, one of my favourites is trying to make every number from 1 to 10, only using calculations that include four 4s. All of the main operation signs can be used as many times as possible and brackets can be used at will! Eg:
[(4x4)/4]/4 = 1 or, you could also do, [(4+4)-4]/4 = 1
(lovely example of the associative law there, too - this is a really good one for illustrating those!)
I believe it can actually be done for all numbers up to 20, but there's a few numbers I still can't work out! Get to work maths boffins!

I also like the puzzle where you substitute the digits in a times table for letters, and the children have to work out what digit each letter stands for and therefore what times table it is, eg:
H x C = GA
B x C = AI
GG x C = CC
A x C = I
J x C = AE
F x C = HD
GA x C = CI
G x C = C
I x C = HA
GE x C = CE
D x C = AC
C x C = GD

That one is quite a nice easy one, but they keep the kids busy for ages, and really get their brains going! I usually put them in small groups to do this sort of thing, so they can bounce all their ideas off each other, peer learning and all that.

My question is, has anyone got any more of these kinds of maths puzzles? If you have any good ones that you think would be good to use with my kids then post away, let me know! It doesn't matter if you think you've got one that's a bit too hard for primary school, because there's usually a way to make it simpler, or it might lead to an idea of something similar I could do. I'd love to hear about ANYTHING anyone's got that I can add to my database of brain stimulating activities!

Get posting, maths boffins! Go go go!

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Martijn
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Re: Maths Puzzles

Post by Martijn » Thu Aug 13, 2009 4:09 pm

oxo_foxo wrote:OK, this is probably a really inappropriate post to put in the 'boffins' section
Oh, no, I think it is very appropriate. Much more interesting anyway than people showing off about hard theorems they have only just entered in the computer (ahum). I've been trying to make ten using four fours since last night but, so far, have failed.

I don't really know good resources for maths puzzles, but I'm sure Google will help you find loads of them. If I come across any I'll promise to post them here. What age are the children you're teaching?

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Martijn
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Re: Maths Puzzles

Post by Martijn » Wed Aug 19, 2009 1:31 pm

(In the end I had derived that it wasn't possible to make ten and then I googled and then it turned out that I had interpreted the rules too strictly. Damn.)

Here's a nice one I just read. Someone's racing two equal rounds on a circuit. During the first round his (average) speed is 50mph. What should his (average) speed during the second round be so that the average speed over both rounds is 100mph?

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indiehorse
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Re: Maths Puzzles

Post by indiehorse » Wed Aug 19, 2009 4:35 pm

Martijn wrote:(In the end I had derived that it wasn't possible to make ten and then I googled and then it turned out that I had interpreted the rules too strictly. Damn.)
I did the same.
Martijn wrote:Here's a nice one I just read. Someone's racing two equal rounds on a circuit. During the first round his (average) speed is 50mph. What should his (average) speed during the second round be so that the average speed over both rounds is 100mph?
It depends on the length of the course, no?
Edit: Actually, I retract this. Or I might not. Still thinking about it...

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frogblast
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Re: Maths Puzzles

Post by frogblast » Thu Dec 10, 2009 1:05 am

Any people who enjoy maths puzzles and computer programming should have a look at Project Euler

It has kept me entertained for quite a while (I've solved 94 problems so far, and I'm ranked 9th in all of Scotland, wohoo!). Some of the problems are just about writing an efficient brute force algorithm, but as they get harder more of them require clever solutions. I started doing them as a way to learn basic programming (I didn't know about the modulus operator before I started, never mind things like linked lists) but now I'm kind of addicted.
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indiehorse
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Re: Maths Puzzles

Post by indiehorse » Tue Jan 29, 2013 2:15 pm

Dear Anoraks, I am stuck on a logic problem at work. Can anyone help?

It's for an orienteering website we develop and they want to introduce this league thing. Competitors run a number of races and are awarded points depending on where they finish. Each competitor belongs to a club. A club may have any number of competitors. The club's points are obtained by taking the highest possible score of 15 competitors in that club, where at least 5 of the competitors are male, at least 5 are female and there at least 3 competitors from each of 4 specified age classes.

How do I go about ensuring that the 15 players that are counted are the 15 that give the highest total without having to iterate through every possible combination of competitors?

Nicole Diver
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Re: Maths Puzzles

Post by Nicole Diver » Tue Jan 29, 2013 2:18 pm

Sort it in descending value of the scores and then pick them perhaps? I'm less sure about how you do the next bit though.

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