Computed 90° − 72° = 18°, mistakenly assuming the angle is the complement.
PRIMARY 5 · MATHEMATICS
Geometry
Top 5 mistakes
Ranked by how often they appear across 43 MOE-aligned practice questions in our archive.
Assumed angle ABC equals angle DAB because they are both angles of the parallelogram (confusing adjacent with opposite angles).
Doubled angle DAB (2 × 72° = 144°), perhaps confusing with an exterior or reflex relationship.
Sums to 190°, exceeds 180°.
Sums to 170°, not 180°.
Want to fix these mistakes for your child?
Superholic Lab's quiz engine flags every misconception by name and routes your child to targeted practice in our 3-day Plan Quest. Free 7-day trial.
Start a free 7-day trial →