Hi Todd! On Tue, 10 Jul 2018 02:02:45 -0700 ToddAndMargo <toddandma...@zoho.com> wrote:
> Hi All, > > Remembering from my school days, a famous mathematician > whose name I forget came up with a formula as a kid > that made math history. > See https://en.wikipedia.org/wiki/Arithmetic_progression . They tell this story about https://en.wikipedia.org/wiki/Carl_Friedrich_Gauss - see http://www.coolmath.com/algebra/19-sequences-series/06-gauss-problem-arithmetic-series-01 , but the formula for that predates him by many centuries. > As it transpires, when in school, they disciplined him by > making his count all the number from 1 to some large > number. It took him only a few minutes. They thought > he cheated, so they sent him back with an even larger > number to add up. Same couple of minutes. Blew his > teacher's minds every number they gave him. > > Seems he had discovered that if you laid the number > out forward, then reverse underneath > > N=5 > > 1 + 2 + 3 + 4 + 5 = 15 > 5 + 4 + 3 + 2 + 1 = 15 > --------------------- > 6 6 6 6 6 = 30 > > If you add the columns, you always got N+1 and N times. > And that make the formula > > 1+2+3..N = (N+1)*N/2 > > I always have fun recreating this formula from the > forward and reverse tables added as columns. > > So feed the following an integer and have fun! > > Yup. He blew his teacher's mind! > > -T > > > $ echo "5" | p6 'my $N=slurp(); say $N*($N+1)/2;' > 15 > > $ echo "6" | p6 'my $N=slurp(); say $N*($N+1)/2;' > 21 > > $ echo "100" | p6 'my $N=slurp(); say $N*($N+1)/2;' > 5050 -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ Chuck Norris/etc. Facts - http://www.shlomifish.org/humour/bits/facts/ I’d love to change the world, but they won’t give me the source code. — Unknown Please reply to list if it's a mailing list post - http://shlom.in/reply .
