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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 236 · 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 57° and 24°. What is the exterior angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 69° and 59°. What is the exterior angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 25° and 50°. What is the exterior angle (in degrees)?
  5. 5.In triangle ABC, angle A = 21° and angle B = 58°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 20° and angle B = 69°. What is angle C (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.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 40° and angle B = 69°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 74° and 51°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 3 cm, 12 cm and 13 cm? (a) No (b) Yes
  17. 17.Can a triangle have sides of 5 cm, 9 cm and 8 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 70° and angle B = 46°. What is angle C (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 73° and 40°. What is the exterior angle (in degrees)?
  20. 20.Can a triangle have sides of 8 cm, 2 cm and 9 cm? (a) No (b) Yes
  21. 21.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  22. 22.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 10 cm, 6 cm and 3 cm? (a) Yes (b) No
  25. 25.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  26. 26.An exterior angle of a triangle is 146°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 2 cm and 8 cm? (a) No (b) Yes
  30. 30.The two interior opposite angles of a triangle are 58° and 52°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 21° and angle B = 137°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 72° and 78°. What is the exterior angle (in degrees)?
  35. 35.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)?
  36. 36.Can a triangle have sides of 2 cm, 11 cm and 12 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 74° and 27°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  39. 39.Can a triangle have sides of 4 cm, 6 cm and 2 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 93° and angle B = 65°. What is angle C (in degrees)?

Answer key

  1. 81
  2. 128
  3. 75
  4. 75
  5. 101
  6. 65
  7. 91
  8. 15
  9. 24
  10. 100
  11. 34
  12. 71
  13. 24
  14. 48
  15. 125
  16. Yes
  17. Yes
  18. 64
  19. 113
  20. Yes
  21. 13
  22. 50
  23. 65
  24. No
  25. 5
  26. 67
  27. 54
  28. 34
  29. Yes
  30. 110
  31. 22
  32. 34
  33. 43
  34. 150
  35. 7
  36. Yes
  37. 101
  38. 40
  39. No
  40. 22

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