Rex's ransom


The purpose of this activity is for students to apply metric units of length, volume, and mass to solve a problem in context.

Achievement Objectives
GM5-1: Select and use appropriate metric units for length, area, volume and capacity, weight (mass), temperature, angle, and time, with awareness that measurements are approximate.
GM5-2: Convert between metric units, using decimals.
Description of Mathematics

The background knowledge presumed for this task is outlined in the diagram below:

This activity should be used in a ‘free exploration’ way with an expectation that students will justify the solutions that they find.


Your beloved Rottweiler, Rex, is kidnapped by an international gang.

The criminals ring with a ransom demand.

You are to drop off $1,000,000 in US $100 notes at a discrete location.

The money must be packed tightly into one briefcase.
Is that possible?

If you can, how much will the briefcase weigh?

The procedural approach (show more)

  • The student finds a way to enclose $100 banknotes into a briefcase without considering how the number of notes might be maximised and calculates the mass of the banknotes using appropriate place value.

The conceptual approach (show more)

  • The student uses a systematic strategy to find the optimal dimensions of a briefcase so the maximum number of notes can be arranged in each layer.

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