Inspiration needed!

[Bumpinthenight]

Please help!

I have an interview and have to teach some Y5 pupils for 30 mins on:

Ma3, 2a: Recognise that angles on a straight line total 180 degrees/know that the sum of the angles of a triangle total 180 degrees.

How can I make this interesting? I really want to just say "lines on a straight line total 180 degrees as does the sum of the angle of triangles so deal with it". Obviously that isn't going to take 30 mins or appeal to all learners, but I suppose I could write it on a whiteboard!

I do have one idea of giving the children a triangle and then getting them to cut off the points and making a straight line.

Any more ideas or inspirations would be gratefully received!

[unreasonableismyname]

Give them each a big sheet of newspaper. Get them to close their eyes and draw three dots. Anywhere (but on the paper, obv :)). Join the dots to make a triangle. Cut out and hold up triangles of all shapes and sizes. Now get them to write down (in secret) on a piece of paper what they think the sum of their corner angles is. Get them to hold up their answers. Find the smallest answer and talk about why the kids think that may or may not be right for that kids' triangle. Ditto for the largest answer. Then get the kids to gently rip off the three corners, stick them down (together, so you can add the angles) on a piece of paper and now ask the same question - talk about who's changed their answers and why. Get them all to hold up their stuck on three corners and get them to come to the conclusion of the lesson without telling them it.

??

[betterwhenthesunshines]

Sorry, but why are you asking for help on this. If you can't think of an interesting way of teaching it, then you should not be going for this job

This is an easy one - a triangle is a physical shape that you can interpret all sorts of ways. How are you going to deal with algebra????

[Bumpinthenight]

Thanks for your suggestion unreasonableismyname I currently have 80 triangles ready to be cut up!!

betterwhenthesunshines because.

Long answer - I had a mental block. There are far more interesting topics that I could have been asked to do where I would have had some inspiration. I don't know the prior knowledge of the chn and I thought other people might come up with a wow idea that I hadn't thought of. I have much better previously planned lessons I could have used, unfortunately they are not needed and this subject was given.

[unreasonableismyname]

Good luck!

btw it's imperative that they tear the corners off the triangle rather than cut. Otherwise, at least 50% of the class will forget which corners of the three little triangles were corners on the big triangle...

And when you add those up, you won't get 180, and it'll all go horribly wrong!!!

Either that, or put red dots right in the corners of the big triangle, or some kind of label, so that it's impossible for the students to mess up :)