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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 218 · 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 2 cm, 12 cm and 8 cm? (a) Yes (b) No
  2. 2.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  3. 3.Can a triangle have sides of 2 cm, 6 cm and 5 cm? (a) Yes (b) No
  4. 4.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 44° and angle B = 47°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  7. 7.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)?
  8. 8.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 15 cm, 8 cm and 11 cm? (a) Yes (b) No
  11. 11.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)?
  12. 12.In triangle ABC, angle A = 53° and angle B = 93°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 51° and angle B = 90°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 54° and 26°. What is the exterior angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  24. 24.Can a triangle have sides of 2 cm, 4 cm and 3 cm? (a) No (b) Yes
  25. 25.The two interior opposite angles of a triangle are 45° and 37°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 24° and angle B = 108°. What is angle C (in degrees)?
  29. 29.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)?
  30. 30.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 5 cm and 6 cm? (a) Yes (b) No
  33. 33.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 72° and angle B = 49°. What is angle C (in degrees)?
  36. 36.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)?
  37. 37.In triangle ABC, angle A = 61° and angle B = 76°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 76° and 29°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 68° and angle B = 44°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?

Answer key

  1. No
  2. 10
  3. Yes
  4. 23
  5. 89
  6. 18
  7. 5
  8. 25
  9. 50
  10. Yes
  11. 24
  12. 34
  13. 53
  14. 5
  15. 36
  16. 14
  17. 39
  18. 63
  19. 84
  20. 49
  21. 76
  22. 80
  23. 30
  24. Yes
  25. 82
  26. 90
  27. 66
  28. 48
  29. 8
  30. 27
  31. 22
  32. Yes
  33. 45
  34. 36
  35. 59
  36. 12
  37. 43
  38. 105
  39. 68
  40. 16

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