# PE exam: situations in which two question choices are close to my final answer: how to pick one?

Consider this question:

I solve this eventual question and my answer is 7.29667:

Among the question choices are 7 x 7 ft and 7.5 x 7.5 ft. Which one should I choose? I guess if a safety margin is intended, the larger choice i.e. 7.5 x 7.5 ft should be selected. Am I right?

There are situations like this in which two question choices are close to my final answer and I'm not quite sure which one to pick. Is considering safety margin a good criterion to pick the choice? Thanks for your help!

• An aside: I like to think I'm quite well-read, but I've never before encountered the name "unit weight" used for the quantity that ISO 80000-1 would call "weight density". Is that common in some circles? May 13 '21 at 9:44
• @DanielHatton Why would you expect civil engineers in the USA to care about ISO? "We don't need no stinkin' international stamdards!" :) May 13 '21 at 11:54
• @alephzero I have read the occasional American document: like I said, I've never encountered that nomenclature. May 13 '21 at 12:02
• It's civil. Round up! May 13 '21 at 13:08