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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 602 · 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.

NameDateTime takenScore ___ / 40
  1. 1.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)?
  2. 2.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 15 cm, 11 cm and 4 cm? (a) No (b) Yes
  4. 4.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  5. 5.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 36° and 48°. What is the exterior angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 93° and angle B = 34°. What is angle C (in degrees)?
  9. 9.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 75° and angle B = 81°. What is angle C (in degrees)?
  12. 12.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)?
  13. 13.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  15. 15.In triangle ABC, angle A = 83° and angle B = 26°. What is angle C (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  17. 17.The two interior opposite angles of a triangle are 41° and 44°. What is the exterior angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  19. 19.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  20. 20.In triangle ABC, angle A = 36° and angle B = 38°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  25. 25.Can a triangle have sides of 3 cm, 13 cm and 11 cm? (a) No (b) Yes
  26. 26.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 68° and 22°. What is the exterior angle (in degrees)?
  30. 30.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 97° and angle B = 45°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 3 cm, 7 cm and 6 cm? (a) Yes (b) No
  36. 36.The two interior opposite angles of a triangle are 39° and 51°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  39. 39.In triangle ABC, angle A = 85° and angle B = 56°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?

Answer key

  1. 7
  2. 22
  3. No
  4. 18
  5. 33
  6. 84
  7. 50
  8. 53
  9. 60
  10. 20
  11. 24
  12. 12
  13. 48
  14. 17
  15. 71
  16. 25
  17. 85
  18. 26
  19. 26
  20. 106
  21. 70
  22. 120
  23. 51
  24. 72
  25. Yes
  26. 28
  27. 37
  28. 54
  29. 90
  30. 76
  31. 38
  32. 55
  33. 20
  34. 11
  35. Yes
  36. 90
  37. 114
  38. 39
  39. 39
  40. 32

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