pranavanmaru Posted October 5, 2015 Share Posted October 5, 2015 I was browsing the web to find intriguing questions for quant section especially in Combinatorics. Bumped on to the following question. How many ternary strings of length 4 have exactly one 1? [Courtesy : http://web.eecs.utk.edu/~booth/311-04/notes/combinatorics.html] My answer for this question was, _,_,_,_ 4 spaces needs to be filled with 0,1 and 2 out of which one of them needs to be 1. there are 4 ways in which one of them could be 1 and in all other instances there would be choices of 2 numbers in filling 3 of these blanks 4*(23) 32 strings have exactly one 1 in it. According to the site where i got this question from though, the answer is different. [3*(23)] Can anyone clarify what's the logical fallacy in my answer? or elaborate more on why it could be wrong? Quote Link to comment Share on other sites More sharing options...
Brent Hanneson Posted October 5, 2015 Share Posted October 5, 2015 How many ternary strings of length 4 have exactly one 1? Way out of scope for the GRE. Cheers, Brent - Greenlight Test Prep Quote Link to comment Share on other sites More sharing options...
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