Answer Key — HSG.CO.C.9

For parents and tutors

Do not share with students before practice tests.

Practice Problems — Sets 1–10

| Set | Guidance | | --- | --- | | Set 1 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 2 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 3 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 4 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 5 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 6 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 7 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 8 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 9 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 10 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. |

Practice Problems — Sets 11–20

| Set | Guidance | | --- | --- | | Set 11 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 12 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 13 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 14 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 15 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 16 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 17 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 18 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 19 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. | | Set 20 | Prove theorems about lines and angles — verify written work and accept reasonable drawings. |

Review tiers 1–10

• Checklists are parent-judged.
• Written items: verify against practice set patterns.
• Standard text: Prove theorems about lines and angles. Theorems include: vertical angles are congruent; when a transversal crosses parallel lines, alternate interior angles are congruent and corresponding angles are congruent; points on a perpendicular bisector of a line segment are exactly those equidistant from the segment's endpoints.

Practice test scoring

| Tier | Pass guidance | | --- | --- | | 1–3 | Most oral tasks smooth; majority of written correct | | 4–6 | 7/10+ total with clear understanding | | 7–8 | 9/12+ with explanations | | 9–10 | Near-perfect; ready to move on |

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