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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 939 · 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 two interior opposite angles of a triangle are 48° and 51°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  3. 3.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)?
  4. 4.The two interior opposite angles of a triangle are 30° and 69°. What is the exterior angle (in degrees)?
  5. 5.In triangle ABC, angle A = 65° and angle B = 45°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 30° and 79°. What is the exterior angle (in degrees)?
  8. 8.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)?
  9. 9.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  11. 11.Can a triangle have sides of 11 cm, 9 cm and 20 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 52° and angle B = 34°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 50° and angle B = 60°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 45° and angle B = 106°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 55° and angle B = 46°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  20. 20.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)?
  21. 21.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 35° and angle B = 25°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 63° and 23°. What is the exterior angle (in degrees)?
  29. 29.Can a triangle have sides of 18 cm, 7 cm and 9 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) No (b) Yes
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 34° and 67°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 65° and angle B = 54°. What is angle C (in degrees)?
  34. 34.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  35. 35.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  40. 40.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)?

Answer key

  1. 99
  2. 30
  3. 24
  4. 99
  5. 70
  6. 50
  7. 109
  8. 15
  9. 90
  10. 13
  11. No
  12. 94
  13. 63
  14. 86
  15. 75
  16. 70
  17. 29
  18. 79
  19. 100
  20. 7
  21. 24
  22. 44
  23. 45
  24. 66
  25. 120
  26. 74
  27. 50
  28. 86
  29. No
  30. Yes
  31. 20
  32. 101
  33. 61
  34. 26
  35. 63
  36. 18
  37. 116
  38. 98
  39. 20
  40. 8

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