Always like a bit of maths and we had it in spades this week.
So roulette wheel sum as a short cut to me would be (1+36)*(202) = 666
Was there a short cur for 12 days of Christmas? 1*12+2*11...+12*1? Split at 6*7 and double but it still took me 30 +2 seconds to work it out!
Anyone do this? Am I simply getting old and slow?
12 days of maths
 Geoff Abell
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Re: 12 days of maths
You forgot to add the zeros for the roulette wheel.

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Re: 12 days of maths
Apparently what you need is the 12th tetrahedal number (the sum of the triangular numbers up to the 12th).
The formula for the nth tetrahedral number is (n x (n + 1) x (n + 2))/6.
For n = 12, this gives (12 x 13 x 14)/6 = 364
Even I had known and remembered the formula I don't think I could have done the arithmetic in 30 seconds, but I suppose it's technically possible.
https://www.mathscareers.org.uk/article ... christmas/
[In this case the calculation reduces to 13 x 14 x 2 (i.e. 26 x 14 or 13 x 28), which I suppose is a bit more feasible in 30 secs.]
The formula for the nth tetrahedral number is (n x (n + 1) x (n + 2))/6.
For n = 12, this gives (12 x 13 x 14)/6 = 364
Even I had known and remembered the formula I don't think I could have done the arithmetic in 30 seconds, but I suppose it's technically possible.
https://www.mathscareers.org.uk/article ... christmas/
[In this case the calculation reduces to 13 x 14 x 2 (i.e. 26 x 14 or 13 x 28), which I suppose is a bit more feasible in 30 secs.]
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