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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 613 · 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 shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  2. 2.Can a triangle have sides of 8 cm, 14 cm and 4 cm? (a) Yes (b) No
  3. 3.Can a triangle have sides of 4 cm, 7 cm and 3 cm? (a) Yes (b) No
  4. 4.The two interior opposite angles of a triangle are 33° and 62°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 78° and angle B = 44°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 40° and 37°. What is the exterior angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 26° and 51°. What is the exterior angle (in degrees)?
  11. 11.Can a triangle have sides of 10 cm, 7 cm and 19 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 81° and angle B = 70°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 72° and 21°. What is the exterior angle (in degrees)?
  18. 18.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 68° and 21°. What is the exterior angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  21. 21.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  22. 22.In triangle ABC, angle A = 49° and angle B = 20°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 68° and 51°. What is the exterior angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 59° and 33°. What is the exterior angle (in degrees)?
  28. 28.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  29. 29.In triangle ABC, angle A = 27° and angle B = 84°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 76° and angle B = 23°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.Can a triangle have sides of 5 cm, 4 cm and 12 cm? (a) No (b) Yes
  34. 34.In triangle ABC, angle A = 20° and angle B = 79°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 10 cm and 10 cm? (a) No (b) Yes
  39. 39.In triangle ABC, angle A = 62° and angle B = 56°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?

Answer key

  1. 20
  2. No
  3. No
  4. 95
  5. 68
  6. 54
  7. 58
  8. 42
  9. 77
  10. 77
  11. No
  12. 29
  13. 40
  14. 12
  15. 28
  16. 72
  17. 93
  18. 21
  19. 89
  20. 90
  21. 71
  22. 111
  23. 45
  24. 18
  25. 68
  26. 119
  27. 92
  28. 50
  29. 69
  30. 71
  31. 81
  32. 17
  33. No
  34. 81
  35. 45
  36. 52
  37. 64
  38. Yes
  39. 62
  40. 28

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