Sunday, April 19, 2009


What do you see here?
9. MacArthur Lock is 80 feet wide.
Right angles.
Either I hadn't prepared my class for this or else I had trained them too well.
Show us. Where are those? What else do you see?

A prism.
Parallel lines.
After a few more conversations along this line.

Is that really the first thing you see when you look at this? Because the first thing I see is a boat.

Oh, yeah. I see that too.
Last week was a rough one for me. I'd done enough prepartion the weekend before that I could coast until Friday. But Thursday night I was not up for planning. Most classes needed to practice. There were worksheets I could photocopy. It wasn't going to be a day I was proud of, but I'd get through it.

I wanted to do something better for my Geometry class. We'd gone over basic formulas for volume on Thursday. The dozen practice problems felt too light to me. I flipped through the textbooks on my shelf for inspiration.

The textbook problem (Geometry Concepts and Skills by McDougal Littel)
Lake Superior is about 22 feet higher than Lake Huron. In order for ships to safely pass from one lake to the other, they must go through one of the four Soo Locks. 

Water is added to the MacArthur Lock until the height is increased by 22 feet. To find the amount of water added to the lock find the volume of a rectangular prism with a length of 800 feet, a width of 80 feet, and a height of 22 feet.

How many gallons of water are added to the MacArthur Lock to raise the ship to the level of Lake Superior? Use the fact that 1 cubic ft~7.5 gal.
I've read Dan's evangelism about What Can We Do With This? and rants against textbooks enough to see a good set-up.

During my prep, I found a couple of photos of the lock. I pulled them into Keynote. I memorized a couple of numbers, tagged an animation of how locks worked for good measure.

After the class had finished listing what they saw in the original photo I flipped to the second. Same lock. No boat. And the water level was lower. 
What's going on here?

The boat's gone.

The buildings are gone.
Yeah, this was last minute. I didn't find the perfect pictures shot at the same angle. We acknowledged that.
What else happened?

The ground's higher.

No, the water's lower.
These aren't classes that are usually that engaged. But all my students were involved in this discussion. Someone in each class knew what a canal was and could describe how it worked. I never used that animation.

I asked them what the math question was. They went for volume. I asked them what information they needed and provided it as they asked. Happily the numbers I memorized were in different units.

I enjoyed that different periods were more varied than I usually have while both reached the major objectives. One of the classes converted to gallons the other was happy to leave it in cubic feet. In one class we estimated the width of the boat and how much wiggle room it had in the canal, the other class didn't inspire that question.
So how did you like this method compared with the usual?

I really liked it! Look at how much we got done! It's like we've already done all our homework.
And then they chased each other around the room instead of practicing a few more problems. Guess I can't win all the time.


Kate Nowak said...

heehee "the first thing I see is a boat."

Can we have the Keynote please? Would be a shame if we couldn't all exploit your nice work. :-)

Sarah Cannon said...

I put the PDF on The keynote itself isn't loading over my school connection. Though that's for editing purposes--I make my stuff on my Mac, project off school's PC. Everything gets exported as PDF's, sad for animations, but Powerpoint is less predictable.

Sarah Cannon said...

And the keynote file can be your's here.

Kate Nowak said...

much obliged, ma'am. :)

Carol said...

Reminds me of the children's sermon joke "It sounds like a squirrel but it must be Jesus."

Sarah Cannon said...

I thought about the same joke as I was writing it. But decided it wasn't worth telling in the post. Glad it wasn't just me thinking it.