Grade 8 · Math

8th grade Missing angles with letters: straight lines, corners and crossing lines worksheet

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Missing angles with letters: straight lines, corners and crossing lines

Grade 8 Math Worksheet - Challenge Me

NameDate

Circle the best answer, or write your answer on the line.

Noah folds a paper strip so that three angles, (x + 5)°, (2x + 10)° and (3x + 15)°, sit side by side along its straight edge. How many degrees is the largest angle?
Pia draws two rays from one point on a straight line on paper, making three angles: (2x)°, (3x + 10)° and (4x + 8)°. How many degrees is the largest angle?
In Ren's paper sketch, three paths leave one point on a straight road, making angles of (x + 14)°, (2x − 5)° and (5x − 5)°. How many degrees is the largest angle?
Tala opens two doors from one hinge line against a straight wall, making angles of (3x + 6)°, (2x + 14)° and (4x − 2)°. How many degrees is the largest angle?
Ari draws a square corner on paper and splits it with one ray. One part is 10° less than three times the other. How many degrees is the bigger part?
Bo's ramp board makes two angles with the flat ground. One is 5° more than four times the other. How many degrees is the bigger angle?
Jun's scissor blades cross. Two angles side by side are (4x + 10)° and (2x + 20)°. How many degrees is the angle across from the (2x + 20)° angle?
Kira draws two roads crossing on paper. Two angles side by side are (5x + 15)° and (3x + 5)°. How many degrees is the angle across from the (3x + 5)° angle?
Luz draws two lines crossing on a clock face. Side by side are (3x + 24)° and (2x + 6)°. How many degrees is the angle across from the (2x + 6)° angle?
Two paper creases cross on Milo's sheet. Side by side are (6x − 6)° and (2x + 26)°. How many degrees is the angle across from the (2x + 26)° angle?

8th grade Missing angles with letters: straight lines, corners and crossing lines worksheet – printable — Print: 1 2 3 4 5 6

About this worksheet

Missing angles with letters: straight lines, corners and crossing lines. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

I can tell from a sketch whether two angles are equal (across from each other), add to 180° (side by side on a line) or add to 90° (a square corner), and write the equation.
I can solve for x when both angles have x, and then find the angle the question asks for.
I can turn a word description into angle expressions and solve it.

Standard: state-only (CCSS 7.G.B.5)

Words to know

vertical angles: Angles across from each other where two lines cross: they are equal.

supplementary: Two angles that add to 180°, like side by side on a line.

complementary: Two angles that add to 90°, filling a square corner.

adjacent: Side by side, sharing a ray.

expression: A rule with x, like (3x + 12)°, standing for an angle.

Common mistakes

Your child mixed up angles across from each other with angles side by side. Angles across from each other at a crossing are equal; angles side by side on a straight line add to 180°.

Your child used 180° where the angles fill a square corner (90°), or 90° where they lie along a straight line (180°). Look for the square-corner mark or the straight line together.

Your child stopped before dividing. After taking the number away, the x term still has a number in front of it: divide by it to find one x.

Questions parents ask

What is the most common mistake with missing angles with letters: straight lines, corners and crossing lines?

Your child mixed up angles across from each other with angles side by side. Angles across from each other at a crossing are equal; angles side by side on a straight line add to 180°.

Are these 8th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

More grade 8 math

See all grade 8 math

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