use estimation to determine if a length or volume measurement is reasonable;
http://quizzer.eduplace.com/cgi-bin/quizzer2.cgi?ID=hmm05_ep/gr5/1707&GRADE=5&UNIT=6&START_QUIZ=1
http://quizzer.eduplace.com/cgi-bin/quizzer2.cgi?ID=hmm05_ep/gr5/1706&GRADE=5&UNIT=6&START_QUIZ=1
http://www.beaconlearningcenter.com/WebLessons/AreWeThereYet/default.htm
http://www.linkslearning.org/Kids/1_Math/2_Illustrated_Lessons/2_Estimation_of_Length/index.html
http://harcourtschool.com/activity/elab2004/gr5/28.html