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maths poser from my 12 year old - why is -1 * -1 = +1
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Posted 2 years ago #
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He won't need to know any of this to get 3 stars at McDonalds
Posted 2 years ago # -
Try to take it out of the maths context:
"I am going..." = Positive
"I am not going..." = NegativeHere's how it works:
"I am not NOT going..." = Negative * Negative = Positive
If you're not, "not going" then you're going. Hence, positive. This is how I explained it to myself some years ago. Dunno if it's right or not but it beats pages of mathematical proof.
Posted 2 years ago # -
The really awesome thing is that now we're past 41 posts the title on the forum page reads:
"maths poser from my 12 year old - why is -1 * -1 = +1 - 2"Posted 2 years ago # -
keep it simple
3 * 4 = 12
-4 * 2 = -8
2 * 4 = 8-4 * 1 = -4
1 * 4 = 4-4 * 0 = 0
0 * 4 = 0-4 * -1 = 4
-1 * 4 = -4-4 * -2 = 8
-2 * 4 = -8-4 * -3 = 12 All about patterns when you look at it. (go down the columns not across BTW).
HTH
Posted 2 years ago # -
-4 * -1 = 4
It was OK up until that point in my non mathematical brain.
Anyway havent the bankers been using the two negatives = a positive up until recentley ?Posted 2 years ago # -
1 * 1 = 1
(2 - 1) * (2 - 1) = 1
4 - 2 - 2 † ( -1 * -1 ) = 1
-1 * -1 = 1off course there's a few more assumptions in there
Posted 2 years ago # -
I never understood how you could calculate the area of a circle using PI since PI is an unknown quantity.
In calculating the area of a circle with a radius of 1 - the the area would be:
3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679
8214808651328230664709384460955058223172535940812848111745028410270193852110555964462294895493038196
4428810975665933446128475648233786783165271201909145648566923460348610454326648213393607260249141273
724587006606315588174881520920962829254091715364367892590360011330530548820466521384146951941511609................................. to infinity and beyond!!Posted 2 years ago # -
PI is an unknown quantity.
No it's not - it's an irrational and transcendental number, but there are ways to calculate it http://en.wikipedia.org/wiki/Leibniz_formula_for_piPosted 2 years ago # -
There may be formulas for calculating Pi but all the digits for Pi haven't been calculated yet....... will they ever be? My point is if you use Pi to calculate the area of a circle you'll get an indefinite string of numbers - not very accurate!
Posted 2 years ago # -
all the digits for Pi haven't been calculated yet....... will they ever be?
Er, by definition no!if you use Pi to calculate the area of a circle you'll get an indefinite string of numbers - not very accurate!
It depends what you mean by accurate. Compared to the accuracy with which you can measure things in the real world it's very accurate. Meanwhile it's quite easy to add a few more digits every time you feel the need for a bit more accuracy. You do realise that if your circle contained all the atoms in the known universe, adding or removing one atom would make more difference to the accuracy than the last digit in the first line of your digits (you have 3 more lines)?OK, so you might argue you want an accurate mathematical answer - the thing is, a mathematician would say that the area of a circle radius 1 is pi (they're not really into numbers)!
Posted 2 years ago # -
In calculating the area of a circle with a radius of 1 - the the area would be: 3.1415926535...
but how would you know what the radius was ? By the time you've measured it, some of the vernier has rubbed off...
Posted 2 years ago # -
as a professional measurement geek i'm loving the way this thread has gone!
Posted 2 years ago #
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