standard_description: Apply properties of operations as strategies to multiply and divide. (Students need not use formal terms for these properties.) ^( )Examples: If 6 × 4 = 24 is known, then 4 × 6 = 24 is also known. (Commutative property of multiplication.) 3 × 5 × 2 can be found by 3 × 5 = 15, then 15 × 2 = 30, or by 5 × 2 = 10, then 3 × 10 = 30. (Associative property of multiplication.) Knowing that 8 × 5 = 40 and 8 × 2 = 16, one can find 8 × 7 as 8 × (5 + 2) = (8 × 5) + (8 × 2) = 40 + 16 = 56. (Distributive property.)
problem_activity: Narrative
The purpose of this activity is for students to estimate the number of shipping containers on a fully loaded cargo ship. Then they make many assumptions about the arrangement of the containers on the boat to come up with a better estimate.
Launch
Groups of 2
Display image.
“How many containers are on the cargo ship?”
“What is an estimate that’s too high?” “Too low?” “About right?”
1 minute: quiet think time
Record responses.
Activity
“A cargo ship can hold many more than 60 containers. The second image is a picture of a cargo ship that is fully loaded.“
5 minutes: independent work time
“Discuss your estimates and assumptions with your partner.”
2 minutes: partner discussion
Monitor for students who are making different assumptions:
The ship is fully loaded.
Some of the space is taken up with structures.
There are more containers below deck that we can’t see.
All containers are the same size.
the specific side lengths of the shipping containers
Student Facing
How many containers are on the cargo ship?
[IMG]
Record an estimate that is:
|                    too low                     |                  about right                   |                    too high                    |
|------------------------------------------------|------------------------------------------------|------------------------------------------------|
| \(\phantom{\hspace{2.2cm} \\ \hspace{2.2cm}}\) | \(\phantom{\hspace{2.2cm} \\ \hspace{2.2cm}}\) | \(\phantom{\hspace{2.2cm} \\ \hspace{2.2cm}}\) |
How many containers are on the cargo ship?
[IMG]
Record an estimate that is:
|                    too low                     |                  about right                   |                    too high                    |
|------------------------------------------------|------------------------------------------------|------------------------------------------------|
| \(\phantom{\hspace{2.2cm} \\ \hspace{2.2cm}}\) | \(\phantom{\hspace{2.2cm} \\ \hspace{2.2cm}}\) | \(\phantom{\hspace{2.2cm} \\ \hspace{2.2cm}}\) |
What assumptions were you making when you came up with your estimates?
Student Response
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Activity Synthesis
Invite students to share their estimates and any assumptions they made.
“How could you improve your estimate?” (Recreate the ship using a model. Check the height, width, and length of the container arrangement. See how many are on one side of the ship and multiply that to get a closer estimate.)


aligns: no