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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 193 · 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.Can a triangle have sides of 8 cm, 10 cm and 17 cm? (a) Yes (b) No
  2. 2.Can a triangle have sides of 9 cm, 21 cm and 11 cm? (a) Yes (b) No
  3. 3.The two interior opposite angles of a triangle are 78° and 53°. What is the exterior angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 56° and angle B = 38°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  9. 9.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 21° and 28°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 4 cm, 7 cm and 11 cm? (a) No (b) Yes
  14. 14.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  15. 15.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  18. 18.In triangle ABC, angle A = 38° and angle B = 113°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 26° and angle B = 68°. What is angle C (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 35° and 42°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 53° and angle B = 62°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 6 cm, 18 cm and 8 cm? (a) No (b) Yes
  24. 24.In triangle ABC, angle A = 69° and angle B = 21°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 3 cm, 3 cm and 4 cm? (a) Yes (b) No
  27. 27.In triangle ABC, angle A = 84° and angle B = 55°. What is angle C (in degrees)?
  28. 28.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)?
  29. 29.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 24 cm, 11 cm and 10 cm? (a) Yes (b) No
  32. 32.In triangle ABC, angle A = 40° and angle B = 84°. What is angle C (in degrees)?
  33. 33.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  34. 34.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  35. 35.In triangle ABC, angle A = 90° and angle B = 20°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 28° and angle B = 43°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?

Answer key

  1. Yes
  2. No
  3. 131
  4. 30
  5. 10
  6. 86
  7. 12
  8. 20
  9. 12
  10. 32
  11. 54
  12. 49
  13. No
  14. 55
  15. 70
  16. 38
  17. 25
  18. 29
  19. 86
  20. 77
  21. 65
  22. 128
  23. No
  24. 90
  25. 29
  26. Yes
  27. 41
  28. 15
  29. 104
  30. 94
  31. No
  32. 56
  33. 8
  34. 17
  35. 70
  36. 53
  37. 24
  38. 109
  39. 69
  40. 73

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