Wow, Isn't maths cool
Discussion
I was helping my 8 year old with her maths homework yesterday.
At school I cant say i really enjoyed maths, but did it out of necessity. anyhow this weeks exercise pointed out how cool maths can be.
Her task this week was long multiplication, nothing special in that really, but then to check her answers she had to find the digital root of the numbers to be multiplied and the digital root of the product. If the sum is correct multiplying the digital roots gives the same number as the digital root of the product the answer to the original sum was correct. It worked every time - waay cool.
Who figures these things out??
As you were
s
At school I cant say i really enjoyed maths, but did it out of necessity. anyhow this weeks exercise pointed out how cool maths can be.
Her task this week was long multiplication, nothing special in that really, but then to check her answers she had to find the digital root of the numbers to be multiplied and the digital root of the product. If the sum is correct multiplying the digital roots gives the same number as the digital root of the product the answer to the original sum was correct. It worked every time - waay cool.
Who figures these things out??
As you were
s
sawman said:
Who figures these things out??
an Indian chap circa WW1 worked it out:http://books.google.co.uk/books?id=GucWm-1OVyMC&am...
fido said:
sawman said:
Who figures these things out??
an Indian chap circa WW1 worked it out:http://books.google.co.uk/books?id=GucWm-1OVyMC&am...
groucho said:
fido said:
sawman said:
Who figures these things out??
an Indian chap circa WW1 worked it out:http://books.google.co.uk/books?id=GucWm-1OVyMC&am...
groucho said:
fido said:
sawman said:
Who figures these things out??
an Indian chap circa WW1 worked it out:http://books.google.co.uk/books?id=GucWm-1OVyMC&am...
e.g. A B which have a and b digits in them .. it reduces the checking to just (a+b) operations.
Remember this was from an age when computers were either non-existent, or incredibly slow. Modern day, I can't think of many uses outside communications (where you need to verify that data has been transmitted/received correctly) but i'm sure loads of useful applications have come from it ..
kma said:
and this is for an 8 year old? is she in mensa or something?
Having moved from a moderately academic school in UK to a highly academic school in Canada she was bored by the lack of challenge in maths so has attending this: http://www.spiritofmath.com/ for a few months and has been really enjoying it. I think the point of this exercise is that it teaches skills the once learnt can be applied in all kinds of complex situations in the future
S
I guessed that digital roots were like logarithms, eg where you add the logs in order to multiply.
However Internet says: 'A digital root is when you add up the digits of a number and what it comes to is the digital root, but if the number it comes to is a two digit number you add the digits up again and you keep doing that until you get a one digit number.eg. 15+ 18 = 33 then you add up the 3 and the 3 together that came from the 33 which = 6, which means the digital root is 6.'
So apart from a Sudoku-stlye trivial mental exercise, I can't think it has much value - or else we'd have done it in the days of 'real' maths
ETA: It's not maths and barely arithmetic, more numbers play I'd say.
NB Chandresekar was pretty big in astronomy - IIRC there's a 'Chandresekhar's Limit' for something.
However Internet says: 'A digital root is when you add up the digits of a number and what it comes to is the digital root, but if the number it comes to is a two digit number you add the digits up again and you keep doing that until you get a one digit number.eg. 15+ 18 = 33 then you add up the 3 and the 3 together that came from the 33 which = 6, which means the digital root is 6.'
So apart from a Sudoku-stlye trivial mental exercise, I can't think it has much value - or else we'd have done it in the days of 'real' maths
ETA: It's not maths and barely arithmetic, more numbers play I'd say.
NB Chandresekar was pretty big in astronomy - IIRC there's a 'Chandresekhar's Limit' for something.
Edited by Simpo Two on Sunday 11th January 15:40
fido said:
sawman said:
Who figures these things out??
an Indian chap circa WW1 worked it out:http://books.google.co.uk/books?id=GucWm-1OVyMC&am...
sawman said:
kma said:
and this is for an 8 year old? is she in mensa or something?
Having moved from a moderately academic school in UK to a highly academic school in Canada she was bored by the lack of challenge in maths so has attending this: http://www.spiritofmath.com/ for a few months and has been really enjoying it. I think the point of this exercise is that it teaches skills the once learnt can be applied in all kinds of complex situations in the future
S
Olf said:
dickb
dly said:
dly said: ok smart arse!!
7 girls get on a bus,
each has 7 bags,
in each bag there is 7 big cats,
each big cat has 7 little cats.
how many legs are on the bus??
i was e-mailed this in the week....
i did work it out, got it right on the 3rd go!!
Do you count the bus driver?7 girls get on a bus,
each has 7 bags,
in each bag there is 7 big cats,
each big cat has 7 little cats.
how many legs are on the bus??
i was e-mailed this in the week....
i did work it out, got it right on the 3rd go!!
dickbdly said:
dly said: ok smart arse!!
7 girls get on a bus,
each has 7 bags,
in each bag there is 7 big cats,
each big cat has 7 little cats.
how many legs are on the bus??
i was e-mailed this in the week....
i did work it out, got it right on the 3rd go!!
Buses don't have legs... 7 girls get on a bus,
each has 7 bags,
in each bag there is 7 big cats,
each big cat has 7 little cats.
how many legs are on the bus??
i was e-mailed this in the week....
i did work it out, got it right on the 3rd go!!
ETA: b
ks...Edited by ih8theesname on Sunday 11th January 16:14
I get 9618 legs... am I right?
my working is thus:
49 cats per bag x 7 per girl = 343 cats per girl x 4 (for cat legs) = 1372 + 2 for the girl = 1374 x 7 = 9618
edited to add
OH ARSE, OF COURSE BUSES DON'T HAVE FRIGGING LEGS
(edited again to say the new Windows 7 calculator is pretty damn nifty!)
my working is thus:
49 cats per bag x 7 per girl = 343 cats per girl x 4 (for cat legs) = 1372 + 2 for the girl = 1374 x 7 = 9618
edited to add
OH ARSE, OF COURSE BUSES DON'T HAVE FRIGGING LEGS
(edited again to say the new Windows 7 calculator is pretty damn nifty!)
Edited by Frederick on Sunday 11th January 16:17
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