Comments on: Problem Two: Pyramids By The Block http://www.tenproblems.com/20061116/problem-two-pyramids-by-the-block/ Exploration, Calculation, Observation: Brain Teasers and Puzzles Fri, 09 Jan 2009 21:18:27 +0000 http://wordpress.org/?v=2.3.2 By: mathieu http://www.tenproblems.com/20061116/problem-two-pyramids-by-the-block/#comment-344 mathieu Sat, 03 Feb 2007 06:06:07 +0000 http://www.tenproblems.com/20061116/problem-two-pyramids-by-the-block/#comment-344 I am not sure why the number is 1029 and not 1015... Shouldn't you solve: 1 + 4 + 9 + ... + i^2 + ... + n^2 = 1015 n * (n+1) * (2n+1) / 6 = 1015 which lead to: n = 14 I am not sure why the number is 1029 and not 1015…
Shouldn’t you solve:

1 + 4 + 9 + … + i^2 + … + n^2 = 1015

n * (n+1) * (2n+1) / 6 = 1015

which lead to:
n = 14

]]> By: xysk http://www.tenproblems.com/20061116/problem-two-pyramids-by-the-block/#comment-311 xysk Tue, 19 Dec 2006 18:24:13 +0000 http://www.tenproblems.com/20061116/problem-two-pyramids-by-the-block/#comment-311 14 ft? 14 ft?

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