Task = Calculate how much water is lost when people brush their teeth.

–       Run a tap for the amount of time it would take someone to brush their teeth and determine how much water is wasted. Estimate prior to experimenting.

–       Find out how much water is used when someone brushes their teeth and only uses the water when necessary.  Estimate prior to experimenting.

–       Use subtraction to find the difference between the two totals.

–       Compare the actual results with your initial estimations.