The purpose of this activity is to engage students in using fractions, proportions and percentages to solve a problem.
This activity assumes the students have experience in the following areas:
The problem is sufficiently open ended to allow the students freedom of choice in their approach. It may be scaffolded with guidance that leads to a solution, and/or the students might be given the opportunity to solve the problem independently.
The example responses at the end of the resource give an indication of the kind of response to expect from students who approach the problem in particular ways.
A class wants to make Flubber.
Their teacher gives them a recipe which uses 4 1/4 cups of water, 4 cups of PVA glue and 4 teaspoons of Borax. She says that they have all the ingredients but only a teaspoon for measuring.
The teacher tells them that Borax makes up 1% of the final mixture, so they should be able to work out how many teaspoons of water and PVA glue to add.
How can the class use this information to work out how many teaspoons in a cup?
The following prompts illustrate how this activity can be structured around the phases of the Mathematics Investigation Cycle.
Introduce the problem. Allow students time to read it and discuss in pairs or small groups.
Discuss ideas about how to solve the problem. Emphasise that, in the planning phase, you want students to say how they would solve the problem, not to actually solve it.
Allow students time to work through their strategy and find a solution to the problem.
Allow students time to check their answers and then either have them pair share with other groups or ask for volunteers to share their solution with the class.
The student uses their knowledge of quarters to create an image for the whole mixture. They rename 4 and 4 ¼ as 33 quarters and relate that to 99%, since the borax is 1% of the mixture. Using a table, the student creates a pattern of equivalent measures to solve the problem.
Click on the image to enlarge it. Click again to close.
The student uses the unit rate that 1% of the mixture equals 4 teaspoons. They recognise that PVA (4 cups) makes up 48% of the mixture so each cup equals 12% of the mixture. Using the unit rate, they calculate 12 x 4 = 48 teaspoons per cup.
Printed from https://meaningfulmaths.nt.edu.au/mmws/nz/resource/making-flubber at 8:52pm on the 26th February 2024