I selected the correct geometric fact, theorem, formula or transformation and used a clear diagram with appropriate labels and units.
Even Better If (EBI)
I will name the fact or theorem, show the substitution or construction step and check whether the size, direction and units of the result are reasonable.
Stretch and deep challenge
Stretch: A rectangle is 9 cm by 12 cm. Find its diagonal and the perimeter of one of the right triangles formed by that diagonal.
Deep challenge: A triangle has sides 8, 15 and 17 cm. Prove it is right-angled and find its area.