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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 534 · 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 = 21° and angle B = 138°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 35° and 43°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 49° and angle B = 67°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 19 cm, 8 cm and 11 cm? (a) No (b) Yes
  6. 6.Can a triangle have sides of 9 cm, 12 cm and 3 cm? (a) Yes (b) No
  7. 7.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 25° and angle B = 72°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 42° and angle B = 62°. What is angle C (in degrees)?
  11. 11.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)?
  12. 12.In triangle ABC, angle A = 37° and angle B = 21°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  16. 16.Can a triangle have sides of 2 cm, 11 cm and 15 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 54° and angle B = 99°. What is angle C (in degrees)?
  19. 19.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)?
  20. 20.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  23. 23.In triangle ABC, angle A = 47° and angle B = 63°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 89° and angle B = 46°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 5 cm and 5 cm? (a) Yes (b) No
  30. 30.The two interior opposite angles of a triangle are 50° and 29°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 6 cm, 8 cm and 17 cm? (a) Yes (b) No
  32. 32.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 61° and 67°. What is the exterior angle (in degrees)?
  34. 34.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  37. 37.Can a triangle have sides of 3 cm, 6 cm and 3 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?

Answer key

  1. 21
  2. 78
  3. 64
  4. 42
  5. No
  6. No
  7. 25
  8. 70
  9. 83
  10. 76
  11. 7
  12. 122
  13. 20
  14. 90
  15. 8
  16. No
  17. 27
  18. 27
  19. 4
  20. 49
  21. 31
  22. 62
  23. 70
  24. 30
  25. 90
  26. 100
  27. 62
  28. 45
  29. Yes
  30. 79
  31. No
  32. 45
  33. 128
  34. 63
  35. 23
  36. 25
  37. No
  38. 45
  39. 134
  40. 46

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