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Year 7 Maths — Lines and angles

Use complementary, supplementary, vertically opposite and parallel-line angle facts.

Name: ________________________

Before you start

Two straight lines cross, and only one of the four angles they make has been given to you. Find out how big each of the others is.

1234
  1. 1. 70° — given
  2. 2. 110° — supplementary
  3. 3. 70° — opposite
  4. 4. 110° — also opposite

Going round the crossing the angles read 70, 110, 70, 110. Each neighbouring pair sits on a straight line and adds to 180°, and each opposite pair is equal — which is the same fact told twice.

  1. 1.Sort each angle as acute or obtuse.

    Groups: Acute · Obtuse

    • 92°
    • 145°
    • 12°
    • 35°
    • 78°
    • 170°

  2. 2.Parallel lines are cut by a transversal. One co-interior angle is 115°. What is the other, in degrees?

  3. 3.Angles round a point add up to how many degrees?

  4. 4.Three angles sit side by side on a straight line. Two of them are 45° and 85°. What is the third, in degrees?

  5. 5.Two straight lines cross. One of the four angles is 130°. What is the angle next to it, in degrees?

  6. 6.Two angles are complementary. One of them is 65°. What is the other, in degrees?

  7. 7.Two angles sit on a straight line, and one is three times the other. How big is the smaller one, in degrees?

  8. 8.When two straight lines cross, the two angles directly opposite each other are always...

    • a) equal
    • b) complementary
    • c) supplementary
    • d) right angles

Answer key — Year 7 Maths — Lines and angles

  1. 1. 35° → Acute; 92° → Obtuse; 78° → Acute; 145° → Obtuse; 12° → Acute; 170° → Obtuse
  2. 2. 65
  3. 3. 360
  4. 4. 50
  5. 5. 50
  6. 6. 25
  7. 7. 45
  8. 8. a) equal