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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 483 · 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.Can a triangle have sides of 11 cm, 5 cm and 9 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 8 cm, 6 cm and 15 cm? (a) Yes (b) No
  4. 4.The two interior opposite angles of a triangle are 55° and 29°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 38° and angle B = 69°. What is angle C (in degrees)?
  7. 7.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)?
  8. 8.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 37° and angle B = 115°. What is angle C (in degrees)?
  10. 10.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)?
  11. 11.In triangle ABC, angle A = 43° and angle B = 47°. What is angle C (in degrees)?
  12. 12.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  13. 13.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 69° and angle B = 56°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 3 cm and 14 cm? (a) Yes (b) No
  21. 21.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 4 cm, 5 cm and 7 cm? (a) No (b) Yes
  27. 27.The two interior opposite angles of a triangle are 71° and 64°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 19 cm, 9 cm and 9 cm? (a) Yes (b) No
  29. 29.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 23° and angle B = 34°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 84° and angle B = 70°. What is angle C (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 78° and 77°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 37° and angle B = 111°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 21° and angle B = 114°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 30° and angle B = 90°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 3 cm, 6 cm and 3 cm? (a) No (b) Yes
  40. 40.The two interior opposite angles of a triangle are 53° and 33°. What is the exterior angle (in degrees)?

Answer key

  1. Yes
  2. 13
  3. No
  4. 84
  5. 76
  6. 73
  7. 15
  8. 90
  9. 28
  10. 7
  11. 90
  12. 8
  13. 92
  14. 102
  15. 20
  16. 21
  17. 46
  18. 72
  19. 55
  20. No
  21. 63
  22. 84
  23. 20
  24. 100
  25. 50
  26. Yes
  27. 135
  28. No
  29. 76
  30. 123
  31. 26
  32. 155
  33. 32
  34. 45
  35. 45
  36. 60
  37. 43
  38. 29
  39. No
  40. 86

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