Students estimate the number of cranberries rather than the number of scoops.
The lesson continues with the
teacher's asking the students to think about how they would estimate the
number of cranberries in the jar. The groups work to determine a value
that represents the number of cranberries in a scoop and how to use that
value to estimate the number of cranberries in a jar. The class comes
back together, and each group shares its value for the number of
cranberries in a scoop. These values range from twenty-one to
twenty-eight cranberries per scoop. In this last video segment, the
students talk about how and why they have come up with different values
for the number of cranberries in a scoop and what single value the whole
class might use as the number of cranberries in a scoop.
----- Transcript Begins ------Teacher: If we are all using cranberries, how can we come up with a different answer? Timmy?Timmy: Because that, um, a cranberry, one of the cranberries, could be bigger than another.Teacher: Yeah.Timmy: Or you could have, um, put it over a little or under a little.Teacher: That's right. Some are bigger, some are smaller. That's just how things work in nature, so Timmy is exactly right. ------ Transcript Ends ----
----- Transcript Begins ------Teacher: What would be an average if we had between twenty-one and twenty-eight? How could we say, like, well the average number was...? What would you say it could be?Boy 2: Twenty-six.Teacher: And why do you say that?Boy 2: Cause, um, there's, there's two twenty-sixes and one and just one of the other numbers.Teacher: Okay, and is there any other reason?There are more twenty-sixes than the others.Emma, what do you think?Emma: It could be like twenty-five because twenty-one is farther is like pretty far apart than twenty-eight and twenty-six and twenty-eight are only separated by one.Teacher: Um, huh.Teacher: So here we say this is the here is our range. We have between twenty-one and twenty- eight. That's what you're saying. And if we wentin to the middle, it would be about twenty-five.------ Transcript Ends -----
can help students develop estimation skills by planning slightly varied
versions of activities, so that students are likely to recognize that
strategies that were successful in one situation may be helpful in the
new tasks.The discussion of an average number of cranberries in a
scoop ends with the selection of a value of twenty-five. The teacher
then relates the counting of multiple scoops to the skip-counting used
when counting quarters to add up to a dollar. The class uses this
counting technique to determine that it takes approximately 300
cranberries to fill a jar.
Roche, Robert . "Cranberry Estimation." In Estimating
produced by WGBH Boston. Teaching Math, A Video Library, K–4. Funded
and distributed by the Annenberg/CPB Math and Science Project, P.O. Box
2345, S. Burlington, VT 05407-2345, 1-800-LEARNER.
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