Jump to content


Photo

The Maths Thread

For Hopeless Cases!

  • Please log in to reply
370 replies to this topic

#16 GMc

GMc

    Prodigy

  • Members
  • PipPipPipPip
  • 1076 posts
  • Member: 322722
    Joined: 27-September 11

Posted 11 March 2014 - 03:12

I am teaching this personally at the moment.  Unfortunately Texas Instruments have moved on from circa 1982 when I did pure and applied maths A levels.  The school issued one is now fluro green and missing the square root button and the x to the power of y button. Perusal of the online manual informs me that the x to the y sign is now the little hat!   The square root requires you to push 2 buttons then the number then enter then an arrow to the right.  Holy cow.  I found DHs calculator in his brief case and everything became much easier.  His is 20 years old and entirely intuitive.  Complete with  square root and x to the power of y buttons.

 

I use little numbers quite often but they have names so you don't have to write the 10 to the power of a negative index.  Things like micrograms and nanograms. 

 

Binary gives me a headache but I guess anything is OK if you use it daily.

 

I am going to send the children to Khan academy and Plymouth uni  and see if they are better than me.  Lets hope so. 


  • 0

#17 dcvos

dcvos

    Advanced Member

  • Members
  • PipPipPip
  • 484 posts
  • Member: 461632
    Joined: 23-May 12
  • Netherlands, near Utrecht

Posted 11 March 2014 - 09:10

I found this maths thread so I wonder if there's anybody who can help me with this maths puzzle.

I like geocaching, gps treasure hunting game. To find this cache I have to solve this maths puzzle. I'm sure there must be some kind of loga rythmic behind it. Can anyone help help me please? (I'm not sure I use the right terms in the translation from dutch, but I think it is clear enough)

 

 

The number exist of 10 numerals
The numerals 0123456789 each come once in the number
The first can be divided bij 1
the number formed bij the first two numerals can be divided bij 2
the number formed by the first  three  numerals can be divided by 3
the number formed by the first four  numerals can be divided by 4
the number formed by the first five numerals can be divided by 5
the number formed by the first six numerals can be divided by 6
the number formed by the first seven numerals  can be divided by 7
the number formed by the first eight numerals can be divided by 8
the number formed by the first nine numerals can be divided
by 9
the number formed bij the ten numerals can be divided by 10

 


  • 0

#18 nigheandonn

nigheandonn

    Newbie

  • Members
  • Pip
  • 24 posts
  • Member: 887771
    Joined: 10-January 14

Posted 11 March 2014 - 10:44

(I usually lurk, but can't resist a puzzle)

 

The last number has to be 0, to divide by 10

xxxxxxxxx0

 

The fifth number has to be 5, to divide by 5

xxxx5xxxx0

 

And the numbers have to go odd-even-odd-even all along, because the numbers that divide by 2, 4, 6 and 8 have to end in an even number.

 

So based on that I made a guess which seems to be right...


  • 0

#19 dcvos

dcvos

    Advanced Member

  • Members
  • PipPipPip
  • 484 posts
  • Member: 461632
    Joined: 23-May 12
  • Netherlands, near Utrecht

Posted 11 March 2014 - 10:54

Yes, I got the 5 and 0, and the odd and even places but then I got stuck.


  • 0

#20 nigheandonn

nigheandonn

    Newbie

  • Members
  • Pip
  • 24 posts
  • Member: 887771
    Joined: 10-January 14

Posted 11 March 2014 - 11:15

At that point I just thought 'I wonder if 9876543210 works'. It seems to!

 

The first three have to divide by 3 if you add them together - that's the only other bit of logic I can think of.


  • 0

#21 dcvos

dcvos

    Advanced Member

  • Members
  • PipPipPip
  • 484 posts
  • Member: 461632
    Joined: 23-May 12
  • Netherlands, near Utrecht

Posted 11 March 2014 - 11:22

But 9876543 / 7 = 14109347, 7  ad not a "whole" number


  • 0

#22 nigheandonn

nigheandonn

    Newbie

  • Members
  • Pip
  • 24 posts
  • Member: 887771
    Joined: 10-January 14

Posted 11 March 2014 - 14:12

Hmm, thought I'd checked that one!

 

Then I think you'll have to start with the first three numbers - how many odd-even-odd combinations can you get from 12346789 which make a number divisible by 3? And do they need to be followed by 2 or 6 or by 4 or 8 to become a 4 digit number divisible by 4?


  • 0

#23 BadStrad

BadStrad

    Virtuoso

  • Members
  • PipPipPipPipPip
  • 3874 posts
  • Member: 88756
    Joined: 28-January 10

Posted 11 March 2014 - 15:14

If I need Pi to more accuracy than 3.14 (and why I would need it is another question) I use this little sentence where the number of letters in each word gives you the numbers of pi.  Sad I know but it makes me smile. . . .

 

How I Wish I Could Calculate Pi

   3 . 1 4 1 5 9 2


  • 1

#24 Norway

Norway

    Virtuoso

  • Members
  • PipPipPipPipPip
  • 4444 posts
  • Member: 452922
    Joined: 05-May 12

Posted 11 March 2014 - 15:21

:hides:  :peace2:

:agree: I want to do colouring.


  • 1

#25 BadStrad

BadStrad

    Virtuoso

  • Members
  • PipPipPipPipPip
  • 3874 posts
  • Member: 88756
    Joined: 28-January 10

Posted 11 March 2014 - 15:45

 

:agree: I want to do colouring.

 

 

You'd be surprised how many A level (maths) students enjoy a bit of colouring in too.


  • 0

#26 Bagpuss

Bagpuss

    Virtuoso

  • Members
  • PipPipPipPipPip
  • 3150 posts
  • Member: 371
    Joined: 07-January 04

Posted 11 March 2014 - 17:32

Oh-oh....I can feel a polynomial coming on....

 

B :) x


  • 2

#27 Barry Toner

Barry Toner

    Advanced Member

  • Members
  • PipPipPip
  • 411 posts
  • Member: 305160
    Joined: 24-August 11
  • Devon

Posted 11 March 2014 - 17:38

Standard form / scientific notation makes doing arithmetic with large numbers much easier, as to multiply to the "power of 10" bits, you simply add the powers, so 100,000 (10^5) times a million (10^6) is 100,000,000,000, or 10^11.  For division, you simply subtract the exponent, so one (proper) billion, which is 10^12, divided by one thousand (which is 10^3), the answer is 10^9.

 

In science, you often have to calculate with big numbers, such as the speed of light, and 2.99792458 * 10^8 m/s is easier to use in calculations that 299,792,458.  The issue of rounding error is more obvious when using scientific notation, as if you use 3 * 10^8 m/s for the speed of light, this is right to within .1%, which may be good enough for your purpose.  Far too many people just read the numbers off the calculator and don't realise that after the first one or two digits, they may have no relevance whatsoever.


  • 0

#28 jim palmer

jim palmer

    Prodigy

  • Members
  • PipPipPipPip
  • 1605 posts
  • Member: 28959
    Joined: 15-April 08
  • South London

Posted 11 March 2014 - 18:12

If I need Pi to more accuracy than 3.14 (and why I would need it is another question) I use this little sentence where the number of letters in each word gives you the numbers of pi.  Sad I know but it makes me smile. . . .

 

How I Wish I Could Calculate Pi

   3 . 1 4 1 5 9 2

Actually you can remember 355 113, and divide the first 3 digits by the second 3. That's very accurate, I got it from one of WW Sawyer's books.

pi_zps2a2572e0.png?t=1394561865


  • 0

#29 cestrian

cestrian

    Advanced Member

  • Members
  • PipPipPip
  • 752 posts
  • Member: 253314
    Joined: 09-May 11
  • Wales

Posted 11 March 2014 - 18:32

Hopefully not drifting too much O/T but I have a book recommendation for anyone who finds this stuff fascinating. It's "Alex's Adventures in Numberland" by Alex Bellos. Read it last year and was captivated from first page to last. The chapter on Vedic Maths was eye-opening to say the least...


  • 0

#30 mel2

mel2

    Virtuoso

  • Members
  • PipPipPipPipPip
  • 4713 posts
  • Member: 6928
    Joined: 15-May 06
  • East Yorkshire

Posted 11 March 2014 - 19:10

The Left and Right thread is filling up with brainy people asserting that an inability to tell L from R doesn't mean they are dim.
Can I say the same thing on here about my failure to understand a word of most of this one, or is that different? I think I need to breathe into a paper bag!
  • 1