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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 58 · 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.

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  1. 1.In triangle ABC, angle A = 45° and angle B = 72°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 23° and 30°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 38° and angle B = 56°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 63° and angle B = 77°. What is angle C (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  7. 7.Can a triangle have sides of 6 cm, 3 cm and 8 cm? (a) Yes (b) No
  8. 8.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  9. 9.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 7 cm, 6 cm and 7 cm? (a) Yes (b) No
  11. 11.Can a triangle have sides of 7 cm, 9 cm and 14 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 7 cm, 12 cm and 4 cm? (a) Yes (b) No
  13. 13.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  18. 18.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 78° and angle B = 51°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 7 cm, 13 cm and 6 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 5 cm, 16 cm and 7 cm? (a) No (b) Yes
  25. 25.The two interior opposite angles of a triangle are 76° and 20°. What is the exterior angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 60° and angle B = 58°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 83° and angle B = 30°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 3 cm, 8 cm and 9 cm? (a) No (b) Yes
  32. 32.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  33. 33.Can a triangle have sides of 7 cm, 9 cm and 17 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 12 cm, 10 cm and 25 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 91° and angle B = 54°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 34° and angle B = 26°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 22° and 80°. What is the exterior angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 63° and 24°. What is the exterior angle (in degrees)?
  39. 39.Can a triangle have sides of 4 cm, 10 cm and 8 cm? (a) Yes (b) No
  40. 40.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?

Answer key

  1. 63
  2. 53
  3. 86
  4. 40
  5. 17
  6. 13
  7. Yes
  8. 24
  9. 37
  10. Yes
  11. Yes
  12. No
  13. 51
  14. 90
  15. 67
  16. 15
  17. 45
  18. 50
  19. 80
  20. 51
  21. No
  22. 120
  23. 13
  24. No
  25. 96
  26. 32
  27. 24
  28. 62
  29. 67
  30. 84
  31. Yes
  32. 67
  33. No
  34. No
  35. 35
  36. 120
  37. 102
  38. 87
  39. Yes
  40. 39

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