Loading...

About Angle Relationships — Class 7 IB

Explore complementary, supplementary, and vertically opposite angles with parallel lines. This topic is part of the IB Class 7 mathematics syllabus (chapter: Unit 5). On this page you can practice 60 questions across three difficulty levels — 20 easy, 20 medium, and 20 hard — each with a visual step-by-step solution, plus a timed 35-question mastery test with a live leaderboard. Worked examples and sample questions from the topic are below.

What you'll learn in Angle Relationships

  • Unlocking Angles: The Basics of Turns and Lines
  • Crossing Paths: Vertically Opposite and Corresponding Angles
  • Hidden Angles: Alternate and Co-interior Relationships
  • Triangle Treasures: Angle Sum and Exterior Angles
  • Beyond Triangles: Angles in Quadrilaterals and Problem Solving

Interactive lesson · about 15 minutes · checkpoint question after every unit

Angle Relationships — solved examples for Class 7 IB

Example 1easy

Angles around a point in a town square are formed by paths intersecting. If three angles measure 75°, 110°, and 90°, what is the measure of the fourth angle?
  1. A)75°
  2. B)85°
  3. C)90°
  4. D)100°

Step-by-step solution

  1. The sum of angles around a point is 360°.
  2. Add the given angles: 75° + 110° + 90° = 275°.
  3. Subtract this sum from 360° to find the fourth angle: 360° - 275° = 85°.
    360°(75°+110°+90°)360° - (75° + 110° + 90°)

Answer: 85°

Example 2medium

Three support beams meet at a central point on a circular platform in a new public park in Geneva. One angle formed between two beams measures 105°, and another angle is 120°. What is the measure of the third angle?
  1. A)A. 115°
  2. B)B. 125°
  3. C)C. 130°
  4. D)D. 135°

Step-by-step solution

  1. Angles around a central point sum to 360°.
  2. Sum of the two given angles = 105° + 120° = 225°.
  3. To find the third angle, subtract the sum of the known angles from 360°.
    Thirdangle=360°225°Third angle = 360° - 225°
  4. Third angle = 135°.

Answer: D. 135°

Example 3hard

Four angles meet at a point O in a complex gear system. The angles are: ∠AOB = (2x + 10)°, ∠BOC = (3x - 5)°, ∠COD = (x + 20)°, and ∠DOA = (4x - 25)°. Find the measure of ∠DOA.
  1. A)A. 105°
  2. B)B. 119°
  3. C)C. 125°
  4. D)D. 135°

Step-by-step solution

  1. The sum of angles at a point is 360°. So, (2x + 10) + (3x - 5) + (x + 20) + (4x - 25) = 360.
  2. Combine like terms: 10x + 0 = 360, which simplifies to 10x = 360.
  3. Solve for x: x = 360 ÷ 10 = 36.
  4. Substitute x = 36 into the expression for ∠DOA: ∠DOA = (4 × 36 - 25)° = (144 - 25)° = 119°.

Answer: B. 119°

Practice questions on Angle Relationships

  1. Q1.easy

    A straight road in Berlin is intersected by a pedestrian crossing. If one angle formed by the intersection on one side of the road is 132°, what is the measure of the adjacent angle on the straight road?
    1. A)38°
    2. B)48°
    3. C)52°
    4. D)62°
    Show answer

    Answer: 48°

    Hint: Angles on a straight line always add up to a specific total. Think about a protractor.

  2. Q2.easy

    When two straight lines intersect, they form four angles. If one of the angles is 65°, what is the measure of the angle vertically opposite to it?
    1. A)25°
    2. B)65°
    3. C)115°
    4. D)180°
    Show answer

    Answer: 65°

    Hint: Vertically opposite angles have a special relationship regarding their measures.

  3. Q3.easy

    In a city grid, two parallel streets, Elm Street and Oak Avenue, are crossed by a transversal road. If the angle formed at the upper-left intersection of Elm Street and the transversal is 110°, what is the measure of the corresponding angle at Oak Avenue?
    1. A)70°
    2. B)90°
    3. C)110°
    4. D)180°
    Show answer

    Answer: 110°

    Hint: Think about the position of corresponding angles relative to the parallel lines and transversal.

  4. Q4.medium

    In the urban planning of a new district in Berlin, a straight main road is intersected by a pedestrian path. If one angle formed between the road and the path is (3x + 10)° and the adjacent angle on the straight road is (2x + 20)°, what is the value of x?
    1. A)A. 30
    2. B)B. 35
    3. C)C. 40
    4. D)D. 45
    Show answer

    Answer: A. 30

    Hint: Angles on a straight line are supplementary, meaning they add up to 180°.

  5. Q5.medium

    Two straight laser beams cross each other in a physics experiment. If one angle formed is 105°, what is the measure of the angle vertically opposite to the adjacent angle on a straight line?
    1. A)A. 75°
    2. B)B. 85°
    3. C)C. 105°
    4. D)D. 115°
    Show answer

    Answer: A. 75°

    Hint: First, find the adjacent angle on the straight line. Then, consider its vertically opposite angle.

  6. Q6.medium

    A designer is planning a pattern for a building facade in Dubai, using parallel lines. If a transversal line intersects two parallel lines, and an angle above the upper parallel line and to the left of the transversal is 130°, what is the measure of the angle below the lower parallel line and to the left of the transversal?
    1. A)A. 130°
    2. B)B. 120°
    3. C)C. 50°
    4. D)D. 60°
    Show answer

    Answer: A. 130°

    Hint: Identify the relationship between the two angles described: they are corresponding angles.

  7. Q7.hard

    A straight beam of light passes through point P, creating three angles on one side: ∠APQ = (x + 10)°, ∠QPR = (2x - 20)°, and ∠RPS = (x + 30)°. Find the value of x.
    1. A)A. 40
    2. B)B. 35
    3. C)C. 37.5
    4. D)D. 42.5
    Show answer

    Answer: A. 40

    Hint: Recall that angles on a straight line sum to 180°. Form an equation with the given algebraic expressions.

  8. Q8.hard

    Two straight lines, AB and CD, intersect at point E, similar to a crosswalk intersection in a European city. Which of the following statements must always be true?
    1. A)A. ∠AEC + ∠DEB = 180°
    2. B)B. ∠AEC and ∠AED are complementary.
    3. C)C. If ∠AEC = 70°, then ∠CEB = 110°.
    4. D)D. ∠AEC + ∠CEB + ∠BED = 360°
    Show answer

    Answer: C. If ∠AEC = 70°, then ∠CEB = 110°.

    Hint: Recall the definitions of vertically opposite angles and angles on a straight line. Consider how these relationships apply to intersecting lines.

  9. Q9.hard

    Lines m and n are cut by a transversal t, resembling a road crossing parallel railway tracks. An angle in the upper-left position where t intersects m is (3x + 30)°. An angle in the lower-left position where t intersects n is (5x - 50)°. For lines m and n to be parallel, what must be the value of x?
    1. A)A. 20
    2. B)B. 30
    3. C)C. 35
    4. D)D. 40
    Show answer

    Answer: D. 40

    Hint: For lines to be parallel, corresponding angles must be equal. Identify the corresponding angles in the given description.

These are 9 of the 60 questions available for Angle Relationships. Start practicing above to unlock visual solutions, AI coaching, and the topic leaderboard — completely free.