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7th grade · Math · Unit 15 of 20

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.

New York State Learning Standards learning standard: NY-7.G.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 New York

In the New York State Learning Standards, this is unit 15 of 20 in 7th grade Math, after Proportional Relationships and before Scale Drawings.

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: New York State Education Department (NYSED)

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

    Two lines cross. One angle is 26°. What is the angle next to it on the same line?

    • 334°
    • 26°
    • 64°
    • 154°

  2. Question 2

    Two angles are supplementary. One is 127°. What is the other?

    • 54°
    • 127°
    • 55°
    • 53°

  3. Question 3

    Three angles sit side by side on a straight line. Two of them are 22° and 68°. What is the third?

    • 270°
    • 68°
    • 90°
    • 88°

  4. Question 4

    Two angles are supplementary. One is x and the other is 3x. What is x?

    • 135°
    • 45°
    • 55°
    • 60°

  5. Question 5

    Three angles sit side by side on a straight line. Two of them are 62° and 68°. What is the third?

    • 130°
    • 28°
    • 50°
    • 230°

  6. Question 6

    Two lines cross. One angle is 86°. What is the angle vertically opposite to it?

    • 4°
    • 94°
    • 86°
    • 274°

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