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7th grade · Math · Unit 15 of 17

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.

Alaska content standards learning standard: 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 Alaska

In the Alaska content standards, this is unit 15 of 17 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: Alaska Department of Education and Early Development

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 angles are complementary. One is 38°. What is the other?

    • 52°
    • 51°
    • 38°
    • 142°

  2. Question 2

    Two lines cross. One angle is 80°. What is the angle next to it on the same line?

    • 80°
    • 10°
    • 100°
    • 280°

  3. Question 3

    Three angles sit side by side on a straight line. Two of them are 42° and 63°. What is the third?

    • 105°
    • 48°
    • 255°
    • 75°

  4. Question 4

    Two angles are supplementary. One is x and the other is 4x. What is x?

    • 45°
    • 144°
    • 36°
    • 46°

  5. Question 5

    Two lines cross. One angle is 30°. What is the angle next to it on the same line?

    • 330°
    • 60°
    • 150°
    • 30°

  6. Question 6

    Three angles sit side by side on a straight line. Two of them are 31° and 61°. What is the third?

    • 268°
    • 92°
    • 88°
    • 59°

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