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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 163 · 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 two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  2. 2.Can a triangle have sides of 3 cm, 3 cm and 9 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 35° and angle B = 89°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 98° and angle B = 39°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 9 cm, 3 cm and 10 cm? (a) Yes (b) No
  6. 6.Can a triangle have sides of 12 cm, 5 cm and 19 cm? (a) Yes (b) No
  7. 7.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  11. 11.In triangle ABC, angle A = 24° and angle B = 99°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  13. 13.In triangle ABC, angle A = 24° and angle B = 116°. What is angle C (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  15. 15.Can a triangle have sides of 10 cm, 10 cm and 6 cm? (a) Yes (b) No
  16. 16.Can a triangle have sides of 18 cm, 5 cm and 8 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 10 cm, 10 cm and 3 cm? (a) No (b) Yes
  19. 19.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  20. 20.The two interior opposite angles of a triangle are 22° and 26°. What is the exterior angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  24. 24.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)?
  25. 25.In triangle ABC, angle A = 34° and angle B = 36°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 69° and angle B = 75°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  31. 31.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 9 cm, 20 cm and 8 cm? (a) No (b) Yes
  33. 33.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  34. 34.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 24° and 63°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  40. 40.In triangle ABC, angle A = 46° and angle B = 52°. What is angle C (in degrees)?

Answer key

  1. 17
  2. No
  3. 56
  4. 43
  5. Yes
  6. No
  7. 51
  8. 30
  9. 54
  10. 32
  11. 57
  12. 57
  13. 40
  14. 25
  15. Yes
  16. No
  17. 73
  18. Yes
  19. 26
  20. 48
  21. 132
  22. 90
  23. 16
  24. 24
  25. 110
  26. 84
  27. 7
  28. 36
  29. 38
  30. 5
  31. 63
  32. No
  33. 39
  34. 80
  35. 87
  36. 77
  37. 20
  38. 38
  39. 25
  40. 82

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