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Tenderloin-
What can I say, I didn't go to school for maths!
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No spreadsheet required...
Imagine a triangle that's got rows of 1, 2, 3, 4 items:-
o
o o
o o o
o o o oNow imagine another triangle upside down that "fits" on top,
o x x x x
o o x x x
o o o x x
o o o o xThis makes a rectangle of 4 x 5
So to add up 1,2,3,4 you can do 4 * (4+1) / 2 = 4 * 5 / 2 = 10.
In general that's n * (n+1) /2
So for 31 you get 31 * 32 / 2 = 496km.
hats
Greenbank
Latest stupid challenge I have taken on is Julyathon - 31 days of running, need to tick off one 1km, one 2km, etc. I agreed to it before I did the maths and realised that it's 450km over the month. Guess it will keep me busy at least. About 10 of us are doing it, some virtually, if anyone else wants to join in then the more the merrier!