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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 437 · 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 10 cm, 5 cm and 15 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  3. 3.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  4. 4.Can a triangle have sides of 17 cm, 6 cm and 6 cm? (a) No (b) Yes
  5. 5.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 69° and angle B = 55°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 97° and angle B = 41°. What is angle C (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 44° and 36°. What is the exterior angle (in degrees)?
  9. 9.Can a triangle have sides of 7 cm, 12 cm and 15 cm? (a) No (b) Yes
  10. 10.Can a triangle have sides of 9 cm, 11 cm and 14 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  15. 15.Can a triangle have sides of 11 cm, 2 cm and 12 cm? (a) No (b) Yes
  16. 16.The two interior opposite angles of a triangle are 58° and 58°. What is the exterior angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  18. 18.Can a triangle have sides of 6 cm, 9 cm and 4 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 21 cm, 10 cm and 10 cm? (a) Yes (b) No
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  22. 22.An exterior angle of a triangle is 146°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 74° and 66°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 31° and angle B = 111°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 46° and angle B = 86°. What is angle C (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  29. 29.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  30. 30.The two interior opposite angles of a triangle are 24° and 24°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 31° and angle B = 46°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 60° and 41°. What is the exterior angle (in degrees)?
  36. 36.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)?
  37. 37.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  39. 39.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?

Answer key

  1. No
  2. 42
  3. 16
  4. No
  5. 17
  6. 56
  7. 42
  8. 80
  9. Yes
  10. Yes
  11. 36
  12. 72
  13. 36
  14. 20
  15. Yes
  16. 116
  17. 20
  18. Yes
  19. No
  20. 90
  21. 12
  22. 75
  23. 120
  24. 59
  25. 140
  26. 38
  27. 48
  28. 80
  29. 18
  30. 48
  31. 103
  32. 26
  33. 104
  34. 44
  35. 101
  36. 24
  37. 50
  38. 30
  39. 52
  40. 13

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