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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 663 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

NameDateTime takenScore ___ / 40
  1. 1.The two interior opposite angles of a triangle are 70° and 70°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 78° and 72°. What is the exterior angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 66° and 35°. What is the exterior angle (in degrees)?
  9. 9.In triangle ABC, angle A = 99° and angle B = 49°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  11. 11.In triangle ABC, angle A = 68° and angle B = 30°. What is angle C (in degrees)?
  12. 12.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  13. 13.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 22 cm, 10 cm and 8 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 72° and 29°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 90° and angle B = 63°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  23. 23.In triangle ABC, angle A = 96° and angle B = 37°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 63° and 31°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 66° and angle B = 50°. What is angle C (in degrees)?
  26. 26.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  27. 27.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  28. 28.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  29. 29.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  30. 30.Can a triangle have sides of 13 cm, 4 cm and 5 cm? (a) Yes (b) No
  31. 31.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  32. 32.In triangle ABC, angle A = 76° and angle B = 79°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 52° and angle B = 32°. What is angle C (in degrees)?
  35. 35.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  36. 36.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 54° and angle B = 50°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 48° and 72°. What is the exterior angle (in degrees)?
  39. 39.Can a triangle have sides of 15 cm, 5 cm and 5 cm? (a) Yes (b) No
  40. 40.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?

Answer key

  1. 140
  2. 72
  3. 150
  4. 90
  5. 30
  6. 76
  7. 20
  8. 101
  9. 32
  10. 63
  11. 82
  12. 18
  13. 90
  14. 45
  15. 118
  16. No
  17. 48
  18. 46
  19. 101
  20. 64
  21. 27
  22. 58
  23. 47
  24. 94
  25. 64
  26. 15
  27. 24
  28. 13
  29. 8
  30. No
  31. 17
  32. 25
  33. 20
  34. 96
  35. 4
  36. 100
  37. 76
  38. 120
  39. No
  40. 52

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