Simple Design Problems
Define a simple design problem reflecting a need or want that includes specified criteria for success and constraints on materials, time, or cost
What a learner can do afterwards
- Define a design problem by describing the need or want it addresses
- Specify at least two criteria for a successful solution, such as holding a stated load and staying upright for a stated time
- Identify constraints such as available materials, time limits, or cost
1 · Read
You have compared designs using goals and test results. Before starting a new design, state the need or want it should meet. A complete plan names that need, gives at least two success rules called criteria, and lists limits called constraints.
Mia needs a model bridge to carry toy cargo across a gap. Her criteria are to hold 6 blocks without bending and stay upright for 20 seconds. Her constraints are 12 straws, one roll of tape and 10 minutes. This is a classroom model, not a bridge for people.
Criteria say what a design must do. Make them clear enough to check. 'Stand without help' is testable without a number. 'Looks nice' needs a clearer judging rule. To compare number targets, count up from the smaller one. From 1 to 6 is five steps, so a target of 6 is 5 more.
Constraints limit what you can use or do, such as materials, time or cost. Here, rules about the design's job are criteria, and building limits are constraints. A $4 cost cap is a constraint here, even though you can check it with a number. A number alone does not tell you the kind of rule.
Turn vague rules into checks. Instead of 'strong enough', say what load it must hold. Test every criterion. A holder that keeps 2 pens inside but falls over does not meet a rule to stand alone. Check the constraints too.
If a plan breaks an agreed limit, revise it and check again. You can ask whether the limit may change, but do not change an agreed rule by yourself. A plan using 9 cards does not fit a limit of 7 cards.
A design problem names the need, gives at least two criteria for success, and lists the constraints on materials, time, or cost.
These four design questions and two readings were written for this learning dataset.
More to read
Plan a carrier for art supplies
The class needs to move art supplies between tables. Before drawing a carrier, they write down that need.
They choose two success rules: the carrier must hold 8 crayons, and none may fall out when the carrier is lifted by its handle.
The available materials are one small carton and two strips of tape. Building time is 12 minutes. These are limits on making the carrier.
A plan could meet the carrying rules but use too much tape. The class needs to check the success rules and the building limits.
Which rules can we check?
A reading group wants a sign that tells visitors when to speak quietly. 'Make a good sign' leaves the group unsure how to judge it.
They agree on two criteria. The sign must stand without anyone holding it. A reader at the doorway must be able to read its words.
Their supplies are one card and two clips. They have 10 minutes to build. These are constraints.
After making the sign, they check each agreed rule. A sign that stands but cannot be read from the doorway still needs a change.
2 · Watch
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Where this leads
12 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.