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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 699 · 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.Can a triangle have sides of 12 cm, 2 cm and 9 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  3. 3.In triangle ABC, angle A = 37° and angle B = 97°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 74° and angle B = 42°. What is angle C (in degrees)?
  9. 9.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 52°. 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 triangle ABC, angle A = 56° and angle B = 24°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 68° and angle B = 33°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  14. 14.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  15. 15.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 5 cm, 16 cm and 9 cm? (a) Yes (b) No
  17. 17.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  19. 19.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 58° and 75°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 27° and angle B = 25°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 2 cm, 14 cm and 8 cm? (a) No (b) Yes
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  32. 32.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 41° and angle B = 94°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 9 cm, 12 cm and 12 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 100° and angle B = 37°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 58° and 65°. What is the exterior angle (in degrees)?

Answer key

  1. No
  2. 74
  3. 46
  4. 20
  5. 68
  6. 13
  7. 45
  8. 64
  9. 73
  10. 100
  11. 100
  12. 79
  13. 13
  14. 30
  15. 38
  16. No
  17. 42
  18. 49
  19. 12
  20. 120
  21. 50
  22. 40
  23. 90
  24. 20
  25. 15
  26. 56
  27. 133
  28. 128
  29. No
  30. 40
  31. 17
  32. 60
  33. 64
  34. 36
  35. 45
  36. 78
  37. Yes
  38. 45
  39. 43
  40. 123

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