Washing detergent proportions

Purpose

The purpose of this activity is to engage students in finding equivalent rates and interpreting the rates in context.

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.

Activity

The Suds company have launched a new detergent. It will come in four bottle sizes, 400 mL, 900 mL, 1.2 L and 2.5 L, to suit customers’ lifestyles. Suds will sell the 1.2 L bottle for $7.80.

What prices should they charge for the other bottle sizes?

Justify why you set those prices.

The procedural approach (show more)

  • The student uses proportional reasoning to establish prices for the three bottles.

The conceptual approach (show more)

  • The student uses proportional relationships and context to establish prices for the three bottles.

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