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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 948 · 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 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)?
  2. 2.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 3 cm, 10 cm and 8 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 45° and angle B = 86°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 80° and angle B = 52°. What is angle C (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 34° and 59°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 9 cm and 18 cm? (a) Yes (b) No
  13. 13.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  14. 14.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)?
  15. 15.Can a triangle have sides of 4 cm, 10 cm and 14 cm? (a) No (b) Yes
  16. 16.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 69° and angle B = 87°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 65° and 45°. What is the exterior angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  21. 21.In triangle ABC, angle A = 43° and angle B = 34°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 35° and angle B = 118°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 30° and 70°. What is the exterior angle (in degrees)?
  24. 24.Can a triangle have sides of 4 cm, 16 cm and 10 cm? (a) No (b) Yes
  25. 25.Can a triangle have sides of 15 cm, 3 cm and 11 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 48° and 28°. What is the exterior angle (in degrees)?
  28. 28.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 23° and 69°. What is the exterior angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  35. 35.Can a triangle have sides of 4 cm, 7 cm and 9 cm? (a) No (b) Yes
  36. 36.Can a triangle have sides of 16 cm, 11 cm and 5 cm? (a) No (b) Yes
  37. 37.In a right-angled triangle, one of the other two angles is 15°. What is the third 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 two interior opposite angles of a triangle are 72° and 76°. What is the exterior angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?

Answer key

  1. 8
  2. 10
  3. 17
  4. Yes
  5. 49
  6. 48
  7. 25
  8. 11
  9. 93
  10. 88
  11. 126
  12. No
  13. 50
  14. 36
  15. No
  16. 39
  17. 24
  18. 110
  19. 15
  20. 20
  21. 103
  22. 27
  23. 100
  24. No
  25. No
  26. 72
  27. 76
  28. 39
  29. 37
  30. 92
  31. 45
  32. 68
  33. 43
  34. 20
  35. Yes
  36. No
  37. 75
  38. 24
  39. 148
  40. 38

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