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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 643 · 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 11 cm, 8 cm and 10 cm? (a) Yes (b) No
  2. 2.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 76° and angle B = 37°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  7. 7.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  8. 8.The two interior opposite angles of a triangle are 21° and 23°. What is the exterior angle (in degrees)?
  9. 9.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 100° and angle B = 21°. What is angle C (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  12. 12.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  15. 15.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  16. 16.In triangle ABC, angle A = 34° and angle B = 43°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 8 cm, 12 cm and 8 cm? (a) Yes (b) No
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  19. 19.Can a triangle have sides of 8 cm, 16 cm and 8 cm? (a) Yes (b) No
  20. 20.In triangle ABC, angle A = 95° and angle B = 22°. What is angle C (in degrees)?
  21. 21.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  22. 22.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 49° and angle B = 87°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 48° and angle B = 98°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 43° and angle B = 55°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  27. 27.The two interior opposite angles of a triangle are 25° and 31°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 26° and angle B = 53°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 37° and 65°. What is the exterior angle (in degrees)?
  30. 30.Can a triangle have sides of 5 cm, 4 cm and 2 cm? (a) No (b) Yes
  31. 31.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  33. 33.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  34. 34.In triangle ABC, angle A = 20° and angle B = 64°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 80° and 72°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  37. 37.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 55° and angle B = 86°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?

Answer key

  1. Yes
  2. 24
  3. 67
  4. 61
  5. 13
  6. 45
  7. 10
  8. 44
  9. 35
  10. 59
  11. 13
  12. 84
  13. 94
  14. 37
  15. 15
  16. 103
  17. Yes
  18. 20
  19. No
  20. 63
  21. 8
  22. 5
  23. 44
  24. 34
  25. 82
  26. 17
  27. 56
  28. 101
  29. 102
  30. Yes
  31. 72
  32. 51
  33. 24
  34. 96
  35. 152
  36. 70
  37. 30
  38. 39
  39. 41
  40. 16

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