Tuesday, August 23, 2011

Magic Expanding Chelonian - Day 3

Here is a compilation of images over the 3 days. The scale was preserved by using the Day 0 chelonian as a reference.  So the question: How valid was the claim it would grow 600%?  Do I need to go back to the $2 shop and demand my money back? Keen to see what my Year 9 maths class makes of this one....

Click for a full size image

Actually - they won't be getting this ready-to-go picture - that's way too easy. Instead they will be offered 4 raw photos of each day, each picture with a Day 0 turtle for scale reference, as well as access to some real-life expanded chelonians if they want to try some hands-on physical measurements.  If this activity works, I might go out and buy another 15 chelonians.


  1. very cool, thanks for the great graphic. I would say they're claim is not that far off. I read the original as being 7x7 boxes. To grow 600% means to get to 7x the size, right? That means that any linear dimension needs to grow to 7x7^(1/3)=13.4 boxes. I read the biggest to be roughly 11x12 boxes which is close. From a percentage perspective, it's interesting that 11 boxes means only a 288% growth and 12 boxes means a 504% growth. I think it comes down to the uncertainty on the "600% growth" claim. Significant figures (ugh, blah, ugh, yuck - sorry, I hate using those) would suggest that the 6 is uncertain. Mostly I'm curious to hear how many of your students fixate on the linear dimensions instead of the volume as I've done. What do you think will happen?

  2. I'm thinking the 600% is good too - if it means volume - which is reasonable. Funny - I just had a debate with someone if 600% means 7x growth or 6x - I'm arguing it means 7. I like your observation about significant figures - my Year 9 did significant figures earlier in the year - be interesting to see what comes up in the discussions.

  3. I'm not predicting anything except a few will be confirmed in their belief they have a v strange teacher - another 'weird activity' :-) I love it!