Big Teeth


The purpose of this activity is to engage students in using a non-standard unit to give a measurement involving fractions.

Achievement Objectives
GM2-1: Create and use appropriate units and devices to measure length, area, volume and capacity, weight (mass), turn (angle), temperature, and time.
GM2-2: Partition and/or combine like measures and communicate them, using numbers and units.
NA2-1: Use simple additive strategies with whole numbers and fractions.
NA2-5: Know simple fractions in everyday use.
Description of Mathematics

In readiness for this problem, the students should have familiarity with each of the following components of mathematics. The problem may be solved with different combinations of these components.

  • length
  • units of length (cm, m)
  • using non-standard units for measurement
  • fractions
  • addition of basic fractions (½, ¼)

This activity may be carried out with guidance, or by allowing the student to follow their own method of solution. The approach should be chosen in sympathy with students’ skills and depth of understanding.



On average the teeth of:
an adult human are 1 ½ cm long.
a great white shark are 7 ½ cm long.

How many adult teeth, stacked end to end, would be needed to make the same length as the great white shark’s tooth?


The arithmetic approach (show more)

  • The student is able to solve a problem using a non-standard units of measurement involving fractions.

The visual approach (show more)

  • The student is able to represent a problem using a non-standard units of measurement involving fractions, leading to a solution.

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