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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 312 · 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.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  2. 2.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  4. 4.The two interior opposite angles of a triangle are 21° and 33°. What is the exterior angle (in degrees)?
  5. 5.In triangle ABC, angle A = 25° and angle B = 132°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 18 cm, 9 cm and 6 cm? (a) No (b) Yes
  7. 7.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 37° and angle B = 81°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 59° and angle B = 92°. What is angle C (in degrees)?
  12. 12.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  14. 14.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)?
  15. 15.In triangle ABC, angle A = 38° and angle B = 86°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 92° and angle B = 27°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 48° and angle B = 96°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  20. 20.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  21. 21.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 70° and 47°. What is the exterior angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 34° and 24°. What is the exterior angle (in degrees)?
  24. 24.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 96° and angle B = 36°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 79° and 74°. What is the exterior angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 77° and 36°. What is the exterior angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  31. 31.The two interior opposite angles of a triangle are 47° and 40°. What is the exterior angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 96° and angle B = 23°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 31° and angle B = 40°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 87° and angle B = 26°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 63° and 68°. What is the exterior angle (in degrees)?
  38. 38.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)?
  39. 39.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)?
  40. 40.In triangle ABC, angle A = 49° and angle B = 78°. What is angle C (in degrees)?

Answer key

  1. 39
  2. 114
  3. 13
  4. 54
  5. 23
  6. No
  7. 17
  8. 62
  9. 66
  10. 20
  11. 29
  12. 15
  13. 90
  14. 15
  15. 56
  16. 34
  17. 61
  18. 36
  19. 45
  20. 12
  21. 17
  22. 117
  23. 58
  24. 48
  25. 48
  26. 153
  27. 113
  28. 25
  29. 60
  30. 25
  31. 87
  32. 16
  33. 50
  34. 61
  35. 109
  36. 67
  37. 131
  38. 24
  39. 24
  40. 53

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