# An unusual way to teach plotting straight line graphs…

I bet you’ve not seen this one before…

There is a linear relationship between air temperature and the number of times a cricket ‘chirps’ per minute. What an interesting idea for a lesson on plotting straight line graphs!

After putting across the idea of the relationship, and motivating the pupils by explaining how the next time they are out and about in the countryside and want to know what the temperature is they can work it out by listening to crickets, give them this worksheet which gets them plotting the linear relationship between degrees fahrenheit and chirps per minute. The worksheet is quite scaffolded and I took some artistic (mathematician’s) license to adjust the coefficients of the equation so that it was more appropriate for secondary school pupils to work with. After working out their table of values and plotting the straight line graph they are given questions that assess their ability to interpret the graph.

If degrees Fahrenheit means nothing to you (because like me, you are English) then you can move the lesson on by giving the pupils this worksheet that gets them plotting the degrees Fahrenheit to degrees Celcius temperature conversion chart. Note the slight increase in pitch with the decimal number coefficient and the negative axes. There are some more interpretation questions to follow once they have completed plotting the graph.

A really nice plenary to this lesson is to get a pupil up at the front and get them to do cricket chirping noises with the rest of the class counting how many they made in a minute. The class then have to use the graphs they have plotted to work out the ‘temperature’ in both degrees Fahrenheit and Celcius.

Great fun and a bit different than teaching this topic from a dry textbook…

It certainly is an interesting linear relationship! I love the idea of the lesson – is there a reason why you didn´t give the students real data to get them to plot the data and find the equation for themselves? Maybe using different variables for the axes would also be an interesting topic of disucssion for low ability.

The plenery is an absolutely brilliant idea!!! 🙂

Hi Dan. Thanks for your comments. It was a long time ago and I’m trying to remember why I didn’t use the real data! Possibly I couldn’t find the actual formula or I ‘dumbed down’ the numbers a little so they didn’t become a learning barrier whilst the kids were focussed on something else. I do agree using real world data would make it more contextual and engaging. If you find the formula could you post it here?!

The formula for this (both celsius & farenheit) appears here:

http://www.snopes.com/science/cricket.asp

It’s a great idea, thanks!

Shouldn’t the independent variable be temperature, and the chirps be the dependent variable?