# NCEES Sample Questions & Solutions, #103 on CPM?



## littlebig (Oct 25, 2010)

Could anyone explain why answers A and B are not correct? Since there is no lag time involved, isn’t LF of activity B equals to LS of activity D (answer A), and ES of activity B equals to EF of activity A (answer B )? Thanks!


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## PEin2010 (Oct 25, 2010)

don't know if this is of much help, but I looked in the CERM for formulas to calculate float. The formula is either LS-ES or LF-EF and substituting accordingly I got the answer to be D:

LS = LF- D

substituting in LS-ES =&gt; float = LF-D -ES

How would you know that there is no lag time involved? it doesn't state so in the problem.


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## littlebig (Oct 25, 2010)

Thanks! Yes, answer D is definitely correct. But I thought A and B are correct too. I thought there was no lag time shown on the diagram, but maybe that is the wrong assumption that I made? What's the difference between the early event time and early start time, and the late event time and late finish time?


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