Which sentence states the need for a design?

• We need a box to keep packed lunches from being squashed.
• We can bend cardboard into several shapes for a lunch box.
• We can buy tape in several colours to use on a lunch box.

A constraint is a limit on materials, time, or cost.

Here, criteria describe the design's job and constraints limit building. Which is a criterion for a model bridge?

• Use only the straws that the teacher provides.
• Hold 5 blocks without bending during the test.
• Finish all the building within the time allowed.

A marker holder has two success rules: keep 3 markers inside and stand without help. Which test checks both rules?

• Load 3 markers, then check that it holds them and stands alone.
• Load 3 markers, then paint it without checking whether it stands.
• Leave it empty, then check its balance without adding any markers.
• Draw 3 markers, then admire the picture without testing the holder.

A tower's job is to stand without help. Building limits are 20 straws and 15 minutes. Which rule is the criterion, not a building constraint?

• Stand up without a person holding the tower.
• Use at most 20 straws from the class supplies.
• Finish building within 15 minutes of starting.

A team writes the tower criterion 'Be strong enough.' Which replacement gives a clear check of its strength?

• Look strong enough for the person who built it to say so.
• Stay upright for 40 seconds with 4 blocks on top.
• Have a name that makes everyone think it is very strong.
• Use a colour that the team thinks looks like a strong tower.

A model must hold 2 blocks and stay upright for at least 30 seconds. A held 2 blocks but fell after 10 seconds. B held 2 blocks and stayed upright for 30 seconds. Which met both criteria?

• Design A: holding the blocks means the time rule can be ignored.
• Both designs: holding the blocks means both time results are enough.
• Design B: it met both success rules in the test.
• Neither design: every model must stand for longer than the stated time.

Two teams write criteria for their boat designs. Team A's boat must hold 4 coins. Team B's boat must hold 7 coins. How many more coins must Team B's boat hold compared to Team A's?

Team A: 'We need to carry toy coins across water. Our boat must float with 5 coins and stay upright for 30 seconds. Use only foil; finish in 20 minutes.' Team B: 'We want to build a boat.' Which plan has the need, two criteria and constraints?

• Team B: wanting a boat already tells us all its success rules and limits.
• Both teams: saying they want a boat means no building limits are needed.
• Team A: it gives the need, success rules and limits.

A team's agreed building limit is 15 minutes. Its plan takes 18 minutes. The limit has not changed. What should the team do next?

• Keep the plan and decide that agreed time limits no longer apply.
• Keep the plan and report 15 minutes even if it takes 18 minutes.
• Keep the plan and change the agreed limit without asking anyone.
• Change the plan so it fits 15 minutes, then check it again.