standard_description: Add and subtract fractions with unlike denominators (including mixed numbers) by replacing given fractions with equivalent fractions in such a way as to produce an equivalent sum or difference of fractions with like denominators. For example, 2/3 + 5/4 = 8/12 + 15/12 = 23/12. (In general, a/b + c/d = (ad + bc)/bd.)
problem_activity: Narrative
The purpose of this activity is for students to estimate whole number products in the context of volume. In the next activity students will calculate the smallest and largest volumes within the range recommended for each type of bird. The estimates here may or may not fall within the range, depending on the numbers students pick. When making reasoned estimates, there is always some tension between accuracy and using the most friendly numbers. During the synthesis, students explain the different strategies they use to make reasonable estimates with calculations that they can perform as simply as possible, often mentally (MP3).
Students may need a quick reminder of how to find the volume of a rectangular prism. If needed, remind students that the volume of a rectangular prism is the product of the length, width, and height, or alternatively, the product of the area of a base and the height for that base.
Launch
Display table from task.
“What do you notice and wonder about the table?” (There are different kinds of birds listed. There are side lengths for the floor but the height is a range. What do the numbers mean? Do smaller birds have smaller houses?)
1 minute: quiet think time
Share and record student responses.
If needed, display images of different kinds of birds.
Activity
2 minutes: quiet think time
5 minutes: partner work time
Monitor for students who consider friendly numbers to use for the height and also for estimating the product of the area of the floor and the height.
Student Facing
Different types of birds use different types of houses. The table gives you the recommended side lengths for birdhouses of various species.
{"table": [{"_attributes": {"border": "1"}, "thead": [{"tr": [{"th": [{"_attributes": {"scope": "row"}, "_value": "type of bird"}, {"_attributes": {"scope": "col"}, "_value": "side lengths of floor"}, {"_attributes": {"scope": "col"}, "_value": "height"}, {"_attributes": {"scope": "col"}, "_value": "volume estimate"}]}]}], "tbody": [{"tr": [{"th": [{"_attributes": {"scope": "row"}, "_value": "chickadee"}], "td": [{"_value": "4 in by 4 in"}, {"_value": "6 to 10 in"}, {}]}, {"th": [{"_attributes": {"scope": "row"}, "_value": "wood duck"}], "td": [{"_value": "10 in by 18 in"}, {"_value": "10 to 24 in"}, {}]}, {"th": [{"_attributes": {"scope": "row"}, "_value": "barn owl"}], "td": [{"_value": "10 in by 18 in"}, {"_value": "15 to 18 in"}, {}]}, {"th": [{"_attributes": {"scope": "row"}, "_value": "red-headed woodpecker"}], "td": [{"_value": "6 in by 6 in"}, {"_value": "12 to 15 in"}, {}]}, {"th": [{"_attributes": {"scope": "row"}, "_value": "bluebird"}], "td": [{"_value": "5 in by 5 in"}, {"_value": "6 to 12 in"}, {}]}, {"th": [{"_attributes": {"scope": "row"}, "_value": "swallow"}], "td": [{"_value": "6 in by 6 in"}, {"_value": "6 to 8 in"}, {}]}]}]}]}
Estimate a possible volume for each birdhouse. Be prepared to explain your reasoning.
Student Response
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Activity Synthesis
“How did you estimate the volume of a house for a wood duck?”
I know
\(10 \times 18\)
is 180 and I multiplied by 10 since that just adds a zero.
I also used
\(10 \times 18 = 180\)
but multiplied by 20 since that is between 10 and 24. I got
\(3,600\)
cubic inches.
“How did you estimate the volume of a house for a red-headed woodpecker?”
I found that the area of the floor is 36 square inches. I multiplied this by 10 to get 360 and by 20 to get 720 and then picked a number in between, 500 cubic inches.
I found the area of the floor was 36 square inches. I rounded that to 40 since it is a nicer number and then found
\(40 \times 12\)
which is 480.
“Which numbers are the friendliest for estimating products? Why?” (10 is the friendliest because I can use place value. Multiples of 10, like 20, are also friendly as I can multiply by 10 and then double.)


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