Identifying possible side lengths
9 in.
marlena has 3 straws. two straws have the lengths
shown. she does not know the length of the shortest
straw, but when she forms a triangle with all three, the
triangle is obtuse. which are possible lengths of the
shortest straw? check all that apply.
12 in.
5 inches
6 inches
7 inches
8 inches
9 inches

the anwser is x< -17/2

• before the lesson, students attempt the assessment task individually. you then review students’

solutions and formulate questions that will them improve their work.

• during the lesson, students work collaboratively in pairs or threes, plotting graphs, completing

tables of values and deducing equations. then, based on the number of common solutions,

students link these representations.

• in a follow-up lesson, students receive your comments on the assessment task and use these to

attempt the similar task, approaching it with insights gained from the lesson.