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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 351 · 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 3 cm, 18 cm and 10 cm? (a) Yes (b) No
  2. 2.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  3. 3.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)?
  4. 4.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 61° and angle B = 79°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 59° and angle B = 72°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 9 cm and 7 cm? (a) Yes (b) No
  12. 12.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 12 cm, 24 cm and 10 cm? (a) No (b) Yes
  17. 17.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  20. 20.The two interior opposite angles of a triangle are 31° and 27°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 57° and angle B = 42°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 80° and angle B = 35°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 35° and 52°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 33° and angle B = 83°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 13 cm, 6 cm and 5 cm? (a) No (b) Yes
  26. 26.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  29. 29.In triangle ABC, angle A = 73° and angle B = 24°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 3 cm, 12 cm and 8 cm? (a) Yes (b) No
  31. 31.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 40° and angle B = 101°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  36. 36.Can a triangle have sides of 20 cm, 12 cm and 4 cm? (a) Yes (b) No
  37. 37.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)?
  38. 38.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 76° and angle B = 20°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?

Answer key

  1. No
  2. 15
  3. 9
  4. 90
  5. 13
  6. 31
  7. 40
  8. 20
  9. 49
  10. 63
  11. Yes
  12. 12
  13. 72
  14. 56
  15. 34
  16. No
  17. 74
  18. 79
  19. 13
  20. 58
  21. 81
  22. 65
  23. 87
  24. 64
  25. No
  26. 38
  27. 54
  28. 16
  29. 83
  30. No
  31. 70
  32. 80
  33. 70
  34. 39
  35. 90
  36. No
  37. 5
  38. 72
  39. 84
  40. 26

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