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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 35 · 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 20° and 23°. What is the exterior angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 76° and 42°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 68° and angle B = 80°. What is angle C (in degrees)?
  5. 5.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  7. 7.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)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  9. 9.In triangle ABC, angle A = 57° and angle B = 67°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 20° and angle B = 79°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 75° and angle B = 23°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 62° and angle B = 65°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 80° and angle B = 35°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 57° and angle B = 39°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 90° and angle B = 48°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  21. 21.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 74° and angle B = 63°. What is angle C (in degrees)?
  25. 25.The longest side of a right-angled triangle is 26 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 45°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 9 cm, 23 cm and 12 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 23° and angle B = 118°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 80° and 31°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 41° and 23°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 91° and angle B = 46°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  33. 33.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  34. 34.Can a triangle have sides of 14 cm, 9 cm and 4 cm? (a) Yes (b) No
  35. 35.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 86° and angle B = 47°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 78° and angle B = 38°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?

Answer key

  1. 43
  2. 118
  3. 57
  4. 32
  5. 51
  6. 90
  7. 7
  8. 23
  9. 56
  10. 81
  11. 82
  12. 62
  13. 53
  14. 65
  15. 84
  16. 46
  17. 42
  18. 88
  19. 79
  20. 39
  21. 36
  22. 33
  23. 40
  24. 43
  25. 10
  26. 45
  27. No
  28. 39
  29. 111
  30. 64
  31. 43
  32. 25
  33. 21
  34. No
  35. 72
  36. 17
  37. 48
  38. 47
  39. 64
  40. 17

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