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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 67 · 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 triangle ABC, angle A = 94° and angle B = 58°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 11 cm, 9 cm and 4 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 73° and angle B = 40°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 3 cm, 9 cm and 14 cm? (a) No (b) Yes
  5. 5.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 54° and angle B = 98°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 77° and angle B = 73°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 47°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 24° and angle B = 69°. What is angle C (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  17. 17.Can a triangle have sides of 20 cm, 6 cm and 12 cm? (a) Yes (b) No
  18. 18.In triangle ABC, angle A = 91° and angle B = 30°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  20. 20.Can a triangle have sides of 5 cm, 12 cm and 5 cm? (a) No (b) Yes
  21. 21.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)?
  22. 22.In triangle ABC, angle A = 92° and angle B = 44°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 60° and 79°. What is the exterior angle (in degrees)?
  25. 25.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  26. 26.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 8 cm, 4 cm and 5 cm? (a) No (b) Yes
  28. 28.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  29. 29.Can a triangle have sides of 7 cm, 12 cm and 13 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 20° and angle B = 25°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 76° and angle B = 72°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  34. 34.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)?
  35. 35.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 42° and 51°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?

Answer key

  1. 28
  2. Yes
  3. 67
  4. No
  5. 60
  6. 24
  7. 78
  8. 100
  9. 28
  10. 36
  11. 26
  12. 30
  13. 22
  14. 48
  15. 87
  16. 17
  17. No
  18. 59
  19. 40
  20. No
  21. 15
  22. 44
  23. 33
  24. 139
  25. 24
  26. 67
  27. Yes
  28. 68
  29. Yes
  30. 135
  31. 32
  32. 60
  33. 13
  34. 8
  35. 52
  36. 40
  37. 93
  38. 45
  39. 130
  40. 36

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