A garden club is designing a bird feeder for the school yard. It must hold 500 milliliters of seed, hang from a branch, and cost no more than five dollars. Which part of that list is a constraint?

Students must build a shelf that holds ten books and costs under eight dollars. Design A holds twelve books and costs ten dollars. Design B holds ten books and costs six dollars. Which design should the team choose?

A team is testing folded paper airplane designs to find which one flies farthest. They want a fair test. Which one thing should be different from flight to flight?

Maya wanted to find which cup keeps water warm longer. She used a plastic cup with a lid and a metal cup with no lid. What is wrong with her test?

A team's cardboard bridge held several coins, then bent and dropped at the spot in the middle where two pieces were taped together. What should the team improve first?

A group rolled a toy car down a ramp one time and measured how far it traveled. Their teacher asked them to repeat the test several more times. Why does repeating the test make the results more trustworthy?

Before a playground is built, a woman who designs it makes a small climbing frame out of straws and clay. How does this model help her?

A class measured how far a rubber band launcher sent a marker. Stretch 5 centimeters: the marker flew 30 centimeters. Stretch 10 centimeters: it flew 62 centimeters. Stretch 15 centimeters: it flew 95 centimeters. What do these measurements show?

Ben claims his homemade sponge soaks up more water than a store sponge. He squeezed his own sponge completely dry first but left the store sponge damp. Why should the class doubt his claim?

A team designing a rain shelter for a bus stop lists these questions: 'What must it do for people waiting?', 'How much can we spend?', 'How many days do we have?', 'Which materials are banned?' Which one asks about a criterion, not a constraint?

A town reports that its playground floods after storms and stays too muddy to use for days. What is the design problem an engineer should solve?

Several groups each built a water filter out of different materials. Why is it useful to compare all of the filters instead of just improving the first one built?

After a test, a team wrote in their journal: the cardboard chair leaned to the left after about half a minute. Why is that a useful note?

A team hangs a small bag of marbles from a spring. The spring stretches only a little more each time a marble is added, so the team needs to compare small differences from trial to trial. Which measuring choice fits that job best?

A class tests two kinds of glue by sticking together strips of the same cardboard. One glued strip is left to dry overnight, and the other is pulled apart after only ten minutes. Which thing must be kept the same to make this a fair test of the glues?

A model rocket design meets every criterion on the list but weighs more than the contest allows. What should the team say about their design?

A club must build a planter that holds 4 kilograms of soil, fits on a 30-centimeter windowsill, and is finished by Friday. Which item on that list is a criterion rather than a constraint?

Two groups test paper towels by dripping water onto a sheet until it stops soaking in. Group A uses 5 drops at a time and Group B uses 20 drops at a time. Why can their results not be compared?

A team's model bridge collapsed at the joint where two strips were taped. They share this test result with another team building a bridge. How does sharing help the other team?

A team should record a test result in its notes even when the result is not what the team expected.