Canteen Price List
Goals:
  • To encourage discussion on the decimal nature of money. 
  • To illustrate the importance of zero in decimals. 
  • To alert students to occasional conflicts between everyday practice and correct mathematics.
Year level:  Year 3 to 8
Group size: Whole Class
Equipment:  An overhead transparency of the 'Canteen Price List' 
Time: Class discussion stimulus - 5 minutes


Activity Instructions: 
1.  Say how much each item on the canteen price list costs and see if they can find any errors.  (There are lollies listed as 0.5 which are actually worth 5c.) Note that this extract was taken from a real canteen list which had been distributed to all students at the school and was probably stuck on 300 home fridges!

2.  Perhaps discuss the "similar" situation of time, e.g. 5 minutes past 3 is 3:05 on a digital clock/watch, not 3:5.  However, while time is similar to decimals of length 2 (in this respect), please remind students that time is not a base ten system!  When counting in minutes, the next time after 3:59 is 4:00 but when counting in hundredths,  3.59 is followed by 3.6. 
 
3.  Follow-up: Students collect examples from daily life where decimal points are used - watching out for any errors.   (Children may also collect examples of 'decimal-point-like' dots which are not decimals so that the class has a range of examples and non-examples.)

Canteen Price List