Stage: 2 Challenge Level: 
You could use a real or model clock and count.
Think how many $5$ minutes are there between the first and tenth bottles falling.
Think how many $5$ minutes are there between the first and tenth bottles falling.
Time. Working systematically. Clock. Mathematical modelling. Interactivities. Speed. Length/distance. Angles. Addition & subtraction. Visualising.
Published March 2003,April 2003.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk