Khan/khan-exercises — Issue #4426: Counting 2 - not consistent grading
Author: KhanBugz
Created: 2011-10-16 17:09:09+00:00
State: open
Labels: firefox, win7

Reporter: johnarmstrongsd@yahoo.com

The first question was exactly the same but instead 13 people and the answer correct was 91; utilizing [n(n+1)]/2. This question with 7 people, the correct answer is 21, solving with [n(n-1)]/2. (not 28) which is a different solution.

[counting_2.html?seed=179&problem=handshakes](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/counting_2.html?seed=179&problem=handshakes&debug)

["28","21"]

Mozilla/5.0 (Windows NT 6.1; rv:7.0.1) Gecko/20100101 Firefox/7.0.1

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