Friday, March 22, 2013

Aliens Have Invaded! Area and Perimeter

Even though we finished up our space unit a few weeks ago, we still needed a biittt longer to banish the aliens finish up our alien area and perimeter unit. Area and perimeter of rectangles/squares is something that was pretty easy for the kids to understand, but it opens up a WHOLE new world for them and for our classroom discussions. 

Throughout this exploration we were connecting our knowledge of multiplication, repeated addition, the commutative property, 2-D shapes, fractions of shapes, adding fractions, adding number strings and subtracting to find the difference. The kids' math vocabulary was flying through the room! I love these moments when all their learning just "clicks." 

Love seeing some addition strategies being used! 

We started off by learning that {ahh! the horror!} we'd been invaded by some very picky moon men.  We'd been studying the moon for quite some time, so it wasn't a big stretch. :) First, we had to design a spaceship so they could get back to the moon as fast as possible. 

Using the partial boxes led to a fun discussion about halves and adding fractions. 

It was going to take quite some time for the aliens' ship to be built, so we had to pick out a fenced in area for them. To do this we had to figure out the amount of space they'd want (moon men like to be close to each other, so we had to pick the smallest area we could). 


We then discussed some perimeter options, including both perimeter of rectangles and non-standard shapes. I was blown away by how quickly they caught on! 

At first I'd mentioned to the class that perimeter can be tricky, because it may seem like we're counting the corner tiles "twice", because we count two sides of the corner tiles. They quickly came up with this solution - measure using the outside! 

We ended with a culminating CHALLENGE problem - to design an area with the maximum amount of perimeter (so the aliens could hang their art) and the smallest amount of area. Their ideas were AWESOME!

One student quickly saw the best way to maximize the difference between his perimeter and area was to figure out how to have as many boxes as possible alone, without touching any of the other boxes. He didn't quite come up with the idea of a diagonal line, but he was close! 


This was a fun and pretty low-prep unit for me. Thanks, aliens. ;)  Up next: geometry (shew!). 

If you're interested in buying this unit - stop by my TpT store! 


  1. This is so clever! We are just starting both units: space and area/perimeter. I never would have thought of combing the two in this way--it's fantastic!

  2. Love the integrated teaching! I am trying to get teachers at my school to move more towards this model. Very engaging for students and a great way to tie all subjects together!!


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