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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 842 · 40 sums
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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 71°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 144°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 51° and 52°. What is the exterior angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 25° and angle B = 81°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 2 cm, 4 cm and 4 cm? (a) No (b) Yes
  9. 9.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  11. 11.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 42° and angle B = 95°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 10 cm, 22 cm and 8 cm? (a) Yes (b) No
  14. 14.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  15. 15.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  16. 16.In triangle ABC, angle A = 58° and angle B = 82°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 5 cm, 11 cm and 4 cm? (a) Yes (b) No
  20. 20.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  22. 22.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)?
  23. 23.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 93° and angle B = 21°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 8 cm, 5 cm and 7 cm? (a) No (b) Yes
  28. 28.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  30. 30.In triangle ABC, angle A = 38° and angle B = 42°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 11 cm, 9 cm and 5 cm? (a) Yes (b) No
  34. 34.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  35. 35.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 52° and 33°. What is the exterior angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?

Answer key

  1. 50
  2. 26
  3. 66
  4. 103
  5. 54
  6. 74
  7. 30
  8. Yes
  9. 52
  10. 72
  11. 54
  12. 43
  13. No
  14. 61
  15. 9
  16. 40
  17. 72
  18. 72
  19. No
  20. 22
  21. 40
  22. 24
  23. 74
  24. 66
  25. 82
  26. 48
  27. Yes
  28. 25
  29. 69
  30. 100
  31. 50
  32. 49
  33. Yes
  34. 24
  35. 13
  36. 72
  37. 40
  38. 85
  39. 19
  40. 20

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