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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 271 · 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.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 17 cm and 11 cm? (a) No (b) Yes
  3. 3.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  5. 5.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  6. 6.In triangle ABC, angle A = 73° and angle B = 77°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 9 cm, 23 cm and 10 cm? (a) Yes (b) No
  8. 8.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  11. 11.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 58° and angle B = 21°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  16. 16.Can a triangle have sides of 23 cm, 12 cm and 10 cm? (a) Yes (b) No
  17. 17.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 45° and angle B = 61°. What is angle C (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 31° and 22°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 71° and angle B = 55°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 3 cm, 12 cm and 4 cm? (a) Yes (b) No
  23. 23.Can a triangle have sides of 3 cm, 11 cm and 10 cm? (a) Yes (b) No
  24. 24.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  25. 25.Can a triangle have sides of 5 cm, 5 cm and 5 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  29. 29.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)?
  30. 30.In triangle ABC, angle A = 63° and angle B = 24°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 58° and angle B = 79°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 5 cm, 13 cm and 5 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.The two interior opposite angles of a triangle are 20° and 66°. What is the exterior angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  40. 40.The two interior opposite angles of a triangle are 41° and 56°. What is the exterior angle (in degrees)?

Answer key

  1. 30
  2. Yes
  3. 100
  4. 52
  5. 51
  6. 30
  7. No
  8. 66
  9. 40
  10. 25
  11. 13
  12. 50
  13. 101
  14. 70
  15. 45
  16. No
  17. 52
  18. 74
  19. 53
  20. 120
  21. 54
  22. No
  23. Yes
  24. 100
  25. Yes
  26. 90
  27. 19
  28. 90
  29. 15
  30. 93
  31. 30
  32. 43
  33. No
  34. 17
  35. 50
  36. 75
  37. 17
  38. 86
  39. 26
  40. 97

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