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7th grade · Math · Unit 14 of 16

Angle Relationships

Complementary, supplementary, vertical

What your child practices

Using complementary, supplementary, vertical and adjacent angles to find a missing angle, sometimes with a simple equation.

Arizona Academic Standards learning standard: 7.G.B.5 · using supplementary, complementary, vertical and adjacent angles to find unknown angles

How we explain it

Children can open this short lesson before they practice.

  1. Complementary angles add to 90°. Supplementary angles add to 180°.
  2. Vertical angles (opposite when lines cross) are equal.
  3. Write an equation and solve for the missing angle.

Example: Two angles are supplementary. One is 65°. What is the other? 180 − 65 = 115. Answer: 115°

Angle Relationships in Arizona

In the Arizona Academic Standards, this is unit 14 of 16 in 7th grade Math, after Proportional Relationships and before Samples & Populations.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Arizona Department of Education

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Three angles sit side by side on a straight line. Two of them are 24° and 51°. What is the third?

    • 66°
    • 285°
    • 75°
    • 105°

  2. Question 2

    Two angles are supplementary. One is 124°. What is the other?

    • 124°
    • 56°
    • 54°
    • 58°

  3. Question 3

    Two angles are complementary. One is x and the other is 2x. What is x?

    • 45°
    • 30°
    • 60°
    • 40°

  4. Question 4

    Two lines cross. One angle is 101°. What is the angle next to it on the same line?

    • 79°
    • 78°
    • 101°
    • 259°

  5. Question 5

    Three angles sit side by side on a straight line. Two of them are 57° and 40°. What is the third?

    • 263°
    • 83°
    • 97°
    • 50°

  6. Question 6

    Two lines cross. One angle is 56°. What is the angle vertically opposite to it?

    • 56°
    • 304°
    • 34°
    • 124°

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