Allday Education

Free Triangle Angle Sum Worksheet

Ten triangle-angle-sum problems: two angles given, find the third. Answer key included.

Answer key included
Name: Date:
Triangle Angle Sum
1.
Two angles of a triangle measure 46∘46^\circ and 98∘98^\circ. Find the measure of the third angle.
2.
Two angles of a triangle measure 25∘25^\circ and 55∘55^\circ. Find the measure of the third angle.
3.
Two angles of a triangle measure 41∘41^\circ and 49∘49^\circ. Find the measure of the third angle.
4.
Two angles of a triangle measure 49∘49^\circ and 104∘104^\circ. Find the measure of the third angle.
5.
Two angles of a triangle measure 20∘20^\circ and 43∘43^\circ. Find the measure of the third angle.
6.
Two angles of a triangle measure 35∘35^\circ and 37∘37^\circ. Find the measure of the third angle.
7.
Two angles of a triangle measure 35∘35^\circ and 120∘120^\circ. Find the measure of the third angle.
8.
Two angles of a triangle measure 38∘38^\circ and 74∘74^\circ. Find the measure of the third angle.
9.
Two angles of a triangle measure 68∘68^\circ and 97∘97^\circ. Find the measure of the third angle.
10.
Two angles of a triangle measure 36∘36^\circ and 117∘117^\circ. Find the measure of the third angle.
Andy · alldayeverydaymath.com
Name: Answer KeyDate:
Triangle Angle Sum
1.
Two angles of a triangle measure 46∘46^\circ and 98∘98^\circ. Find the measure of the third angle.
Answer: 36∘36^\circ
2.
Two angles of a triangle measure 25∘25^\circ and 55∘55^\circ. Find the measure of the third angle.
Answer: 100∘100^\circ
3.
Two angles of a triangle measure 41∘41^\circ and 49∘49^\circ. Find the measure of the third angle.
Answer: 90∘90^\circ
4.
Two angles of a triangle measure 49∘49^\circ and 104∘104^\circ. Find the measure of the third angle.
Answer: 27∘27^\circ
5.
Two angles of a triangle measure 20∘20^\circ and 43∘43^\circ. Find the measure of the third angle.
Answer: 117∘117^\circ
6.
Two angles of a triangle measure 35∘35^\circ and 37∘37^\circ. Find the measure of the third angle.
Answer: 108∘108^\circ
7.
Two angles of a triangle measure 35∘35^\circ and 120∘120^\circ. Find the measure of the third angle.
Answer: 25∘25^\circ
8.
Two angles of a triangle measure 38∘38^\circ and 74∘74^\circ. Find the measure of the third angle.
Answer: 68∘68^\circ
9.
Two angles of a triangle measure 68∘68^\circ and 97∘97^\circ. Find the measure of the third angle.
Answer: 15∘15^\circ
10.
Two angles of a triangle measure 36∘36^\circ and 117∘117^\circ. Find the measure of the third angle.
Answer: 27∘27^\circ
Andy · alldayeverydaymath.com

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About this worksheet

Every problem uses the fact that a triangle's three angles add to 180 degrees. Students subtract the two known angles from 180 — the foundational angle skill that later powers exterior-angle and polygon work.

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