angels Posted June 18, 2004 Share Posted June 18, 2004 What is the sum of first 100 nos. of the following series: X = 1/p - 1/(p+1) P a) 99/100 b) 1 c) 0 d) 100/101 e) 1/100000 Quote Link to comment Share on other sites More sharing options...
simple Posted June 18, 2004 Share Posted June 18, 2004 It is (a) looking at at in " simple" way: 1-(1/2)+(1/2)-(1/3)+(1/3) ........ (1/99)-(1/100)+(1/100)-(1/100) Note that the terms are cancelleing each other, except for the first and the last. 1-(1/100)=99/100 Quote Link to comment Share on other sites More sharing options...
angels Posted June 18, 2004 Author Share Posted June 18, 2004 On second thought, I think the answer should be 100/101 as the 100th term will be (1/100 - 1/101) Therefore, the terms left after cancellation will be: 1 - 1/101 = 100/101 Quote Link to comment Share on other sites More sharing options...
angels Posted June 22, 2004 Author Share Posted June 22, 2004 Can anyone please put some light on the correct answer? Quote Link to comment Share on other sites More sharing options...
ursula Posted June 22, 2004 Share Posted June 22, 2004 Angels, I agree with you that it should be 100/101 The explanation by simple is essentially correct, except for the typo in the very last term. Of course in typical GMAT fashion it turns out to be one of the answer choices to trap you... Quote Link to comment Share on other sites More sharing options...
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