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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 17 · 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.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 26° and 30°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 27° and angle B = 88°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  6. 6.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 70° and angle B = 31°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 44° and angle B = 25°. What is angle C (in degrees)?
  12. 12.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)?
  13. 13.The two interior opposite angles of a triangle are 24° and 63°. What is the exterior angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (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 an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 22° and angle B = 114°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 47° and 28°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 90° and angle B = 53°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 95° and angle B = 42°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 10 cm, 7 cm and 19 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 94° and angle B = 39°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 58° and 65°. What is the exterior angle (in degrees)?
  28. 28.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  30. 30.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)?
  31. 31.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 6 cm, 7 cm and 4 cm? (a) Yes (b) No
  33. 33.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  37. 37.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 10 cm, 16 cm and 6 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 7 cm, 12 cm and 4 cm? (a) Yes (b) No
  40. 40.The two interior opposite angles of a triangle are 28° and 63°. What is the exterior angle (in degrees)?

Answer key

  1. 35
  2. 56
  3. 65
  4. 40
  5. 26
  6. 57
  7. 136
  8. 79
  9. 20
  10. 75
  11. 111
  12. 8
  13. 87
  14. 40
  15. 15
  16. 60
  17. 44
  18. 27
  19. 88
  20. 75
  21. 37
  22. 43
  23. 80
  24. 44
  25. No
  26. 47
  27. 123
  28. 27
  29. 78
  30. 7
  31. 112
  32. Yes
  33. 80
  34. 82
  35. 64
  36. 32
  37. 51
  38. No
  39. No
  40. 91

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