📝 Triangle Theorems: Practice B (G-CO.C.10)

Paginepagineapp.com

Name:

Date:

Prove and apply theorems about triangles (angle sum, exterior angle, isosceles). Solve each problem.

1. A triangle has angles 49° and 63°. Third angle = ___

2. Exterior angle of a triangle; remote interior angles 67° and 32°. Exterior angle = ___

3. Isosceles triangle with vertex angle 80°. Each base angle = ___

4. A triangle has angles 37° and 69°. Third angle = ___

5. Exterior angle of a triangle; remote interior angles 61° and 26°. Exterior angle = ___

6. Isosceles triangle with vertex angle 70°. Each base angle = ___

7. A triangle has angles 43° and 37°. Third angle = ___

8. Exterior angle of a triangle; remote interior angles 52° and 56°. Exterior angle = ___

9. Isosceles triangle with vertex angle 20°. Each base angle = ___

10. A triangle has angles 25° and 60°. Third angle = ___

11. Exterior angle of a triangle; remote interior angles 77° and 41°. Exterior angle = ___

12. Isosceles triangle with vertex angle 52°. Each base angle = ___

Answer key: 1) 68° · 2) 99° · 3) 50° · 4) 74° · 5) 87° · 6) 55° · 7) 100° · 8) 108° · 9) 80° · 10) 95° · 11) 118° · 12) 64°

Love free resources? The free Pagine app tracks the books your child reads — kids earn streaks & badges. 📚 App Store · Google Play

← All worksheets

Free to print & share · pagineapp@mwamb.compagineapp.com

Worksheets › Grade 10 Math (Geometry) › Triangle Theorems › Triangle Theorems

Grade 10 (ages 15–16)Numbers & mathsFree printable PDF

About this grade 10 worksheet

Free Grade 10 Geometry math worksheet (Common Core G-CO.C.10): triangle theorems — a second set of twelve practice problems, with answer key. Skill: Prove and apply theorems about triangles (angle sum, exterior angle, isosceles). Level: Grade 10 — also suits Year 11 (UK).

For teachers: skills & standards

CCSS G-CO.C.10: Prove and apply theorems about triangles (angle sum, exterior angle, isosceles)
Works as a morning-work page, a centre/station activity, homework or an early-finisher task.

Frequently asked questions

Is this worksheet free?

Yes — it is free to print for home or the classroom. Sign in with a free Pagine account, then use the Print button or save it as a PDF.

What age is it for?

It is designed for Grade 10 (ages 15–16), but use it with any child who is ready.

What skills does it build?

Prove and apply theorems about triangles (angle sum, exterior angle, isosceles).

Where can I find grade 10 books to read with it?

Pagine's free library has 20,000+ children's books you can read in the Pagine e-reader or the free Pagine app — sorted by age and grade, with free audiobooks too.

More “Triangle Theorems” printables (g-co.c.10: prove and apply theorems about triangles (angle sum, exterior angle, isosceles))

Triangle Theorems: Practice A (G-CO.C.10) · Triangle Theorems: Mixed Practice & Reasoning (G-CO.C.10) · Triangle Theorems: Show Your Thinking (G-CO.C.10) · Triangle Theorems: Quick Check (G-CO.C.10)

All 5 triangle theorems sheets → · Grade 10 Math (Geometry): all 10 skills → · All Common Core grades

📚 Read along: 20,000+ free books in the Pagine e-reader

Pair this grade 10 worksheet with a story. Pagine's free library has 20,000+ children's books — classic novels, drama, poetry and non-fiction, classics and free audiobooks — that you can read right in the Pagine e-reader on any phone, tablet or computer, with adjustable text size and night mode. No ads.

Browse free grade 10 books → · Grade 10 reading level · Free audiobooks · High school reading list

📱 Get the free Pagine app — log every book your child reads (scan the barcode or search), set reading goals, and watch streaks and badges grow. Download on the App Store · Get it on Google Play