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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 83 · 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 = 95° and angle B = 58°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 63° and 37°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 80° and angle B = 75°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  7. 7.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  9. 9.In triangle ABC, angle A = 74° and angle B = 77°. What is angle C (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  11. 11.Can a triangle have sides of 12 cm, 15 cm and 3 cm? (a) No (b) Yes
  12. 12.Can a triangle have sides of 7 cm, 18 cm and 11 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  17. 17.In triangle ABC, angle A = 63° and angle B = 61°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 4 cm, 11 cm and 20 cm? (a) No (b) Yes
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.Can a triangle have sides of 4 cm, 10 cm and 6 cm? (a) Yes (b) No
  22. 22.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  23. 23.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  24. 24.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 64° and angle B = 81°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 96° and angle B = 55°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  32. 32.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  33. 33.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)?
  34. 34.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)?
  35. 35.Can a triangle have sides of 6 cm, 3 cm and 4 cm? (a) No (b) Yes
  36. 36.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  39. 39.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  40. 40.In triangle ABC, angle A = 61° and angle B = 25°. What is angle C (in degrees)?

Answer key

  1. 27
  2. 27
  3. 100
  4. 25
  5. 36
  6. 39
  7. 70
  8. 5
  9. 29
  10. 17
  11. No
  12. No
  13. 26
  14. 80
  15. 100
  16. 25
  17. 56
  18. 56
  19. No
  20. 40
  21. No
  22. 24
  23. 36
  24. 48
  25. 31
  26. 90
  27. 45
  28. 35
  29. 29
  30. 75
  31. 100
  32. 32
  33. 7
  34. 18
  35. Yes
  36. 50
  37. 41
  38. 64
  39. 56
  40. 94

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