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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 108 · 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 6 cm and 8 cm. How long is the longest side (in cm)?
  2. 2.Can a triangle have sides of 12 cm, 16 cm and 5 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 82° and angle B = 70°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 62° and angle B = 34°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 53° and angle B = 82°. What is angle C (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 73° and 42°. What is the exterior angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  10. 10.Can a triangle have sides of 2 cm, 3 cm and 9 cm? (a) Yes (b) No
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  13. 13.Can a triangle have sides of 13 cm, 8 cm and 2 cm? (a) Yes (b) No
  14. 14.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  15. 15.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  18. 18.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 99° and angle B = 56°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  23. 23.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)?
  24. 24.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  26. 26.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  27. 27.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  31. 31.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  32. 32.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)?
  33. 33.In triangle ABC, angle A = 74° and angle B = 34°. What is angle C (in degrees)?
  34. 34.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  35. 35.Can a triangle have sides of 8 cm, 12 cm and 17 cm? (a) No (b) Yes
  36. 36.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 61° and angle B = 49°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 34° and 20°. What is the exterior angle (in degrees)?
  39. 39.Can a triangle have sides of 2 cm, 9 cm and 10 cm? (a) No (b) Yes
  40. 40.The two interior opposite angles of a triangle are 78° and 27°. What is the exterior angle (in degrees)?

Answer key

  1. 10
  2. Yes
  3. 28
  4. 70
  5. 84
  6. 45
  7. 115
  8. 55
  9. 18
  10. No
  11. 72
  12. 100
  13. No
  14. 12
  15. 31
  16. 78
  17. 90
  18. 22
  19. 48
  20. 45
  21. 25
  22. 50
  23. 8
  24. 40
  25. 69
  26. 9
  27. 62
  28. 122
  29. 72
  30. 57
  31. 26
  32. 24
  33. 72
  34. 66
  35. Yes
  36. 79
  37. 70
  38. 54
  39. Yes
  40. 105

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