Richer Percentages

Monday, 26 April 2010 | 6 Comments

How do you make a unit on percentages richer / project-based / engaging / authentic?

A unit on percentages is one of those where I struggle to connect the messages of far greater “educators” than I with the reality of my classroom. I stick with a fairly standard approach to percentages:

Intro – defining percentages, percentages ↔ fractions (denominator of 100).
Simple fractions to percentages and common percentages.
Percentages as decimals and vice versa.
Finding a percentage of a given quantity.
Comparing like quantities by converting to a given percentages.
Profit/loss as a percentage of cost/selling price.

Real Life problems (really just the same as above using the calculator).

We try to focus on not using a calculator, but rather using a knowledge of common percentages or other mental methods.

Sale catalogue ad with misuse of percentages

In “real-life” percentages are usually already solved for our students – not always correctly though.

The most interesting activity in this series of lessons comes at the end when we consider The Biggest Loser, however – to be honest – the way I’ve presented this only allowed maybe the top 2 students in a class to achieve, certainly needs a re-work for this year.

This is my problem, rich / project / authentic tasks seem to pitch themselves above the capabilities of an average mixed class at my school. Usually meaning that an attempt to undertake such an activity results in a more teacher-led lesson than normal. I say this is my problem, because obviously I need to find/create/borrow activities and ideas that are better suited to my students. But, they just don’t seem to be out there.

So, how do you make a unit on percentages richer / project-based / engaging / authentic?

This is the sort of question I hope anyone can pose on my new Q&A site for maths teachers – a work in progress.

Posted in • How to • Lesson Idea • Percentages | Short URL: http://mths.co/1816

Comments

Brendan Murphy on 26 April 10 at 03:24 PM #

It takes patience and a willingness for students to fail. Sometimes especially at first training students to deal with real, real world problems means letting them struggle for days. The trick is keeping them on task. So ways of doing this is to have select groups share their thoughts each day or a bit more often. Don't give answers no matter how much you want to only let students give each other clues. Good luck.

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Simon Job on 27 April 10 at 02:25 AM #

From "Malyn Mawby":http://malyn.edublogs.org/ on "Twitter":http://twitter.com/ozmawbs/statuses/12874786272 bq. (1) "Percentage Composition":http://malyn.edublogs.org/2010/02/17/percentage-composition/ (also revise Data concepts) & (2) "Vitruvian Man":http://malyn.edublogs.org/2010/02/22/the-vitruvian-man-a-context-for-learning/ is probably better for Rates/Ratio.

Meagan Rodda on 27 April 10 at 11:04 AM #

Simon, there was some good stuff on Tale last time I looked. Designing gardens and school yards where there had to be a certain percentage of the yard as grass etc. The area was divided up into a grid to reinforce the percentage/fraction connection. We have a series of Coles Supermarket lessons where the kids go down and collect data and answer questions. We look at percentage discounts of course as well as percentage of daily intake etc. I know what you mean though. It is something they always struggle with and never seem to understand properly. Tend to work out problems using the algorithm they have been taught rather than through any real understanding.

Liz Hemmings on 27 April 10 at 11:32 AM #

I agree Simon, I really struggle to get the kids at my school to think. As soon as the questions get a little different even if not difficult they get frustrated and give up. I have done some rich tasks before (not in percentages) and they either do nothing or do it all wrong and could care less as long as they are finished. The only classes that seen to benefit are the top class and still only a handful of them.

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Simon Job on 27 April 10 at 11:36 AM #

Meagan, thanks for the reminder about the "design your neighbourhood" activities. I've added them to "Maths Links":http://mathsclass.net/links/category/Percentages/. Beyond the first one "Design a school" which is a 10 by 10 grid, I find that I end up just answering lots of questions.

Meagan Rodda on 01 May 10 at 12:18 AM #

I agree Simon, some of the Tale stuff is often a bit above our bottom students. I also agree with Liz. I think our kids are in the habit of wanting quick answers and not having to think for themselves. A product of the 'Google' age. Not sure how we get them out of it though!! Lots more problem solving at primary school maybe?

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Simon Job — eleventh year of teaching maths in a public high school in Western Sydney, Australia.
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