Browsing reddit, thinking of you, Dan. :D

Also, if you want to make science teacher’s lives easier by teaching weighing-by-difference what I’d do (’cause I’m a science teacher) is:

(1) Show picture of entire coin jar with mass total for coins at bottom.

(2) Hand out sample scoop images with mass of jar listed as what was left AFTER the scoop came out.

Students could then subtract to find the mass of the scoop.
Then on their own, they could set up their own masses to value ratios.

This would add time to the lesson, for sure, but would also really really work them, mathematically.

@Claire Agree with your correction- it’s mass not weight. Surprised that the U.S. Mint has it wrong.

The fact that you’ve shared what
“took a week of detailed planning and an afternoon of careful shooting” is fabulous! Hopefully most folks will be thinking “of course he shared it”, and not just because it’s Dan Meyer. When you put a bunch of effort into a really delicious unit the only thing better than it working really well with your own students is knowing that your effort is paying off for other teachers and their students.

A few questions/comments about specifics:
1. The photo of the first jar of mixed coins, the mass of that one is 6,634 grams right?
2. In the shots where your hand is going in to scoop out coins and the mass of the jar is indicated below, a literal interpretation would be that the mass of all the coins is the printed mass plus the mass of coins in your hand. This isn’t the intent, but does contribute a bit of noise to the visuals. Not sure though that there would be a solution that wouldn’t create distractions of its own.

Cheers!

To me the issue is purely logistic. You may or may not be at a site where you feel comfortable having $75 in change around.

Just to keep managing things simple if I ran this lesson I’d likely stick with pennies for the hands-on part. I’d feel uncomfortable running this with no hands-on at all, because to be honest I feel a little uncomfortable with just the pictures (I don’t have a good feel for what 5500 grams means) so I’m sure some of my students will be too.

Plus, y’know, kinesthetic learners.

There may also be logistics involved in how much time you have to allocate for the lesson. With all the topics a math teacher needs to handle digital may be the only way to squeeze it in here.

One last point is it’s possible to pull an estimate with only the original raw picture, with no weight and no extra scale. What is visible in the picture can be your random sampling, and you can pull out an actual nickel and measure it to get an idea of the scale; then do some geometry to get the volume. It’s a rougher estimate than the weight will give you but it works if you’re teaching Geometry rather than Algebra.

why are we doing this digitally?

It may be because I teach middle schoolers, but my kids really do thrive with stuff they can grab.

I get why parts of this are done digitally – we want predictable answers, we want to be able to highlight the nickels only problem, and we want to avoid having the kids filch quarters to get themselves gatorade during lunch.

Still, It seems that there’s room in this lesson to let at least one kid shove his hand into a jar and pull out a handfull of change.

Oh, and I think it’s a wonderful follow on to the fish problem.