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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 205 · 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 an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 22° and 30°. What is the exterior angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 60° and 73°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 63° and angle B = 80°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 80° and angle B = 69°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 10 cm, 9 cm and 2 cm? (a) No (b) Yes
  7. 7.In triangle ABC, angle A = 37° and angle B = 69°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 41° and angle B = 58°. What is angle C (in degrees)?
  9. 9.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 22° and angle B = 31°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 77° and 27°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 16 cm, 9 cm and 11 cm? (a) No (b) Yes
  16. 16.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 11 cm, 11 cm and 7 cm? (a) No (b) Yes
  19. 19.In triangle ABC, angle A = 50° and angle B = 51°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 21 cm and 11 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 9 cm, 11 cm and 18 cm? (a) Yes (b) No
  22. 22.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  23. 23.The two interior opposite angles of a triangle are 23° and 71°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 5 cm, 13 cm and 4 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 26 cm, 12 cm and 9 cm? (a) Yes (b) No
  28. 28.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  29. 29.In triangle ABC, angle A = 65° and angle B = 45°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 28° and angle B = 76°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  32. 32.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)?
  33. 33.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  40. 40.In triangle ABC, angle A = 34° and angle B = 67°. What is angle C (in degrees)?

Answer key

  1. 96
  2. 52
  3. 133
  4. 37
  5. 31
  6. Yes
  7. 74
  8. 81
  9. 24
  10. 55
  11. 127
  12. 63
  13. 15
  14. 104
  15. Yes
  16. 52
  17. 20
  18. Yes
  19. 79
  20. No
  21. Yes
  22. 25
  23. 94
  24. 43
  25. No
  26. 30
  27. No
  28. 4
  29. 70
  30. 76
  31. 36
  32. 7
  33. 40
  34. 24
  35. 26
  36. 21
  37. 100
  38. 70
  39. 36
  40. 79

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