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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 135 · 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.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  2. 2.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 26° and angle B = 26°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 51° and 37°. What is the exterior angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.The two interior opposite angles of a triangle are 67° and 40°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  11. 11.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  12. 12.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 20° and 71°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 91° and angle B = 44°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 74° and angle B = 59°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 63° and 23°. What is the exterior angle (in degrees)?
  21. 21.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  22. 22.Can a triangle have sides of 8 cm, 16 cm and 3 cm? (a) Yes (b) No
  23. 23.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  24. 24.Can a triangle have sides of 3 cm, 3 cm and 8 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 100° and angle B = 38°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 67° and 28°. What is the exterior angle (in degrees)?
  27. 27.Can a triangle have sides of 8 cm, 9 cm and 5 cm? (a) No (b) Yes
  28. 28.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  31. 31.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)?
  32. 32.The two interior opposite angles of a triangle are 43° and 78°. What is the exterior angle (in degrees)?
  33. 33.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  34. 34.In triangle ABC, angle A = 44° and angle B = 44°. What is angle C (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 57° and angle B = 41°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 2 cm, 16 cm and 10 cm? (a) Yes (b) No

Answer key

  1. 23
  2. 26
  3. 36
  4. 11
  5. 128
  6. 88
  7. 86
  8. 25
  9. 107
  10. 36
  11. 5
  12. 50
  13. 54
  14. 91
  15. 118
  16. 76
  17. 45
  18. 47
  19. 90
  20. 86
  21. 22
  22. No
  23. 100
  24. No
  25. 42
  26. 95
  27. Yes
  28. 5
  29. 62
  30. 15
  31. 15
  32. 121
  33. 76
  34. 92
  35. 38
  36. 22
  37. 78
  38. 82
  39. 66
  40. No

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