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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 181 · 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.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  3. 3.In triangle ABC, angle A = 45° and angle B = 68°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 18 cm, 12 cm and 6 cm? (a) No (b) Yes
  5. 5.In triangle ABC, angle A = 33° and angle B = 103°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  12. 12.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 22° and angle B = 23°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 100° and angle B = 23°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 95° and angle B = 64°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 50°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 18 cm, 5 cm and 12 cm? (a) No (b) Yes
  20. 20.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 17 cm, 8 cm and 8 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  24. 24.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 11 cm, 9 cm and 8 cm? (a) No (b) Yes
  26. 26.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)?
  27. 27.Can a triangle have sides of 7 cm, 12 cm and 5 cm? (a) Yes (b) No
  28. 28.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 59° and angle B = 55°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 89° and angle B = 48°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 75° and angle B = 40°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  37. 37.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  39. 39.In triangle ABC, angle A = 22° and angle B = 61°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?

Answer key

  1. 116
  2. 29
  3. 67
  4. No
  5. 44
  6. 36
  7. 40
  8. 18
  9. 112
  10. 65
  11. 25
  12. 104
  13. 135
  14. 29
  15. 70
  16. 57
  17. 21
  18. 20
  19. No
  20. 64
  21. No
  22. 72
  23. 25
  24. 63
  25. Yes
  26. 7
  27. No
  28. 46
  29. 72
  30. 62
  31. 66
  32. 17
  33. 43
  34. 65
  35. 56
  36. 72
  37. 3
  38. 49
  39. 97
  40. 20

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