Don't even show the kids anything. Don't go and pick up the cup. Simply say to the students:
Students, I will have a cup in my hands very soon. There will be cubes inside. How many cubes do you think will be in the cup?
Okay, look how simple this uninformative setup was. If I were a student, a bunch of questions would have just popped into my head: Hey teacher, what size is the cup? Is it a small paper cup? A medium coffe cup? or a large Big Gulp cup? What size are the cubes? As a fourth grader, I know what base ten cubes look like. Are they bigger like the size of snap cubes? Are they the size of ice cubes? and how about the amount of cubes in the cup, teacher? Are there just two at the bottom? Is the cup half full (or over half empty for you pessimists)? Is the cup full of cubes?
Any number the students produce would simply be a guess. It's a low-entry point, but doesn't hold much strength for long. How many cubes are in the cup? It could be two. It could be two hundred. Two thousand. You get the point. This strategy reminds me of a couple engineering classes I took in which we discussed a black box. In other words, there's something inside this black box that serves a purpose or function. However, you have no idea what's inside or the parts that make it function.
Let's spiffy up our description, but still refrain from showing students the cup, cubes, or content level:
Students, I have a small drinking cup in my hand that's about 8 oz. Inside are cubes that are slightly smaller than six-sided dice. The cup is a little less than half full. How many cubes are inside?
By this time, I hope students would be falling out of their seats trying to sneak a peek at the cup. They're lusting after more information to make a more accurate assessment. You're simply adding some labels to the black box. Heck, put the cup inside a brown paper bag for this part.
Reveal the cup. Take it out of the black box and put it in the display case. That's right, put it in the display case. Don't let them touch it.
ladder of abstraction. I think the key to this is encouraging students to demand more information. Don't inundate them with all of the context clues immediately. Make them demand the clues.
Hands-On is the last stage of estimation. Without counting, allow the students to pick up the cup. I'm not saying students will change their estimate. However, it will give them opportunities to consider another perspective of the task. They are including another component: weight, size, etc. There's only one place to go from the hands-on stage and that's revealing the answer: the payoff.
1-Black box: Keep that description minimal. Avoid a visual.
2-Label the black box: gradually reveal some information
3-Display case: Look but don't touch
4-Hand-On: incorporate one last sense in order to bring one last perspective to the estimate.
By the way, did you know that Stevie Wonder played many of the instruments on his Innervisions album. I read somewhere that he virtually played all the instruments on about six of the nine songs. That's one of my favorite Stevie Wonder albums. If he can do that without the use of sight, imagine what we can do with all of our senses.
Part 3: Why should we be the gatekeeper of information for our students? How can you help your students build their number sense and demand more information to make a reasonable estimation? How do I incorporate estimation in my classroom?