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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 408 · 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 75° and 42°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  4. 4.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)?
  5. 5.The two interior opposite angles of a triangle are 50° and 31°. What is the exterior angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 76° and angle B = 36°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 2 cm, 8 cm and 15 cm? (a) No (b) Yes
  9. 9.In triangle ABC, angle A = 35° and angle B = 34°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 31° and angle B = 33°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 9 cm and 7 cm? (a) No (b) Yes
  12. 12.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  13. 13.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 60° and angle B = 92°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  17. 17.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)?
  18. 18.In triangle ABC, angle A = 34° and angle B = 48°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 35° and 64°. What is the exterior angle (in degrees)?
  22. 22.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  23. 23.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  25. 25.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  26. 26.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 81° and angle B = 33°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 6 cm, 8 cm and 7 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 96° and angle B = 54°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 96° and angle B = 28°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 10 cm, 14 cm and 8 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 52° and 52°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  39. 39.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?

Answer key

  1. 117
  2. 25
  3. 46
  4. 15
  5. 81
  6. 60
  7. 68
  8. No
  9. 111
  10. 116
  11. Yes
  12. 24
  13. 20
  14. 67
  15. 28
  16. 90
  17. 8
  18. 98
  19. 12
  20. 90
  21. 99
  22. 16
  23. 90
  24. 100
  25. 7
  26. 67
  27. 66
  28. Yes
  29. 30
  30. 73
  31. 84
  32. 56
  33. Yes
  34. 50
  35. 72
  36. 138
  37. 104
  38. 50
  39. 52
  40. 75

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