A constraint says the limit

What this lesson teaches: A constraint is a limit on what you may use: the materials, the time, the money or the space.

The script (narration and what is on screen)

#	Narration	On screen
1	Mr. Park's class is designing pencil holders. Mr. Park says, "The holder must keep ten pencils standing." That is a criterion, not a constraint.	Mr. Park's classroom; the ten-pencil cup from L01; speech chip MUST KEEP 10 PENCILS STANDING; chip NOT A CONSTRAINT; no title slide
2	"Use only one sheet of cardboard." That limits the materials. That is a constraint.	one sheet of cardboard beside the cup; speech chip ONLY 1 SHEET OF CARDBOARD; chip CONSTRAINT
3	And, "Finish by the end of the lesson." That limits the time. That is a constraint.	a clock on the wall; speech chip FINISH BY THE END OF THE LESSON; chip CONSTRAINT
4	And, "Spend no more than two dollars." That limits the money. That is a constraint.	two one-dollar bills beside the cardboard; speech chip NO MORE THAN 2 DOLLARS; chip CONSTRAINT
5	And, "It may take no more space than one desk corner." That limits the space. That is a constraint.	a dashed square on the desk's corner; the cup sits inside it; speech chip NO MORE SPACE THAN A DESK CORNER; chip CONSTRAINT
6	But, "It must not tip when the desk is bumped." That is a criterion, not a constraint.	the desk wobbles and the cup stays up; speech chip MUST NOT TIP WHEN THE DESK IS BUMPED; chip NOT A CONSTRAINT
7	So, here's what we've seen. A constraint is a limit on what you may use: the materials, the time, the money or the space. A criterion says what the design must do. A constraint says what you may use.	rule slide reuses the sheet of cardboard, the clock and the dashed desk corner; rule text
8	Okay, now your turn.	the attached question appears

Here is Mr. Park's list of sentences. Some say what the holder must do. Others say what the class may use.

A sentence that says the job

"The holder must keep ten pencils standing up." That is a criterion, not a constraint.

Sentences that set a limit

"Use only one sheet of cardboard." That limits the materials. That is a constraint.

"Finish by the end of the lesson." That limits the time. That is a constraint.

"Spend no more than two dollars." That limits the money. That is a constraint.

"It may take no more space than one desk corner." That limits the space. That is a constraint.

One more sentence that says the job

"It must not tip when the desk is bumped." That is a criterion, not a constraint.

Mr. Park's sentence	Job or limit?	What kind of limit?	It is a …
The holder must keep ten pencils standing up.	job		criterion
Use only one sheet of cardboard.	limit	materials	constraint
Finish by the end of the lesson.	limit	time	constraint
Spend no more than two dollars.	limit	money	constraint
It may take no more space than one desk corner.	limit	space	constraint
It must not tip when the desk is bumped.	job		criterion

A constraint is a limit on what you may use: the materials, the time, the money or the space.

A criterion says what the design must do. A constraint says what you may use.

Okay, now your turn

One easy question straight after the video: the student answers it to move on.

After the video

A class is designing a bird feeder. Which sentence is a constraint?

Quiz

(a) fluency: sort each sentence into the two classes just defined. Fresh contexts, never the lesson's own pencil holder.

Question 1

A class designs a kite. "Use only two sticks and one sheet of paper." Is this a criterion or a constraint?

Question 2

"The kite must stay in the air for ten seconds." Is this a criterion or a constraint?

Question 3

A class designs a seed planter. "The planter must hold the soil in when it is carried." Is this a criterion or a constraint?

Question 4

"Finish the planter by Friday." Is this a criterion or a constraint?

Question 5

A class designs a phone stand. "The stand may use no more space than a pencil box." Is this a criterion or a constraint?

Question 6

"The stand must hold the phone up while a video plays." Is this a criterion or a constraint?

Question 7

A class designs a model bridge. "Spend no more than three dollars." Is this a criterion or a constraint?

Question 8

A limit on the materials, time, money or space a design may use is called a …

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