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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 290 · 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.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  2. 2.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)?
  3. 3.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 66° and 25°. What is the exterior angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  6. 6.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 8 cm and 8 cm? (a) No (b) Yes
  8. 8.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  13. 13.The two interior opposite angles of a triangle are 52° and 72°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 3 cm, 5 cm and 4 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 7 cm, 16 cm and 8 cm? (a) No (b) Yes
  16. 16.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 11 cm, 18 cm and 7 cm? (a) No (b) Yes
  19. 19.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  23. 23.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)?
  24. 24.Can a triangle have sides of 9 cm, 9 cm and 14 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 27° and angle B = 119°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  28. 28.Can a triangle have sides of 15 cm, 11 cm and 4 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 83° and angle B = 50°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  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.Can a triangle have sides of 12 cm, 22 cm and 7 cm? (a) Yes (b) No
  37. 37.In triangle ABC, angle A = 62° and angle B = 49°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  40. 40.In triangle ABC, angle A = 25° and angle B = 122°. What is angle C (in degrees)?

Answer key

  1. 36
  2. 7
  3. 20
  4. 91
  5. 57
  6. 59
  7. Yes
  8. 63
  9. 100
  10. 50
  11. 56
  12. 17
  13. 124
  14. Yes
  15. No
  16. 50
  17. 25
  18. No
  19. 20
  20. 38
  21. 34
  22. 56
  23. 8
  24. Yes
  25. 34
  26. 74
  27. 100
  28. No
  29. 47
  30. 31
  31. 39
  32. 45
  33. 120
  34. 79
  35. 13
  36. No
  37. 69
  38. 20
  39. 76
  40. 33

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